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The water is very clear now but there is still a lot of hair type algae on the plants/glass/driftwood

Hey, what is the color of that hair stuff? Brown or green or white? And - how does it look in detail, like small singular strands (hair algae, strands that branch out (staghorn), or hairs that like to bunch up in groups (diatoms), or what?

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

It's all green. The stuff on the driftwood (the piece on the far right) is very dense, like a carpet. It is individual strands under an inch long, very soft and slippery. Can be pulled up but it is hard to grip it. This algae is also present on the amazon sword and on a small patch on the back glass. There is staghorn algae on various places: the heater cord, some leaves, filter intake... It can get quite a few inches long, feels coarser, holds strongly but can be pulled off completely. The algae that is on most of the glass and a lot of leaves is very short single strands but not carpet like. It looks just like the staghorn, but not segmented.

Baoh lioness,

It seems like you have pretty much all algae types collected in your tank, not so good.

The little dense hair mats are often fixed by removing the affected leaves, or if hardware then by taking that piece out and scrubbing it off with Excel.

The other two (if one is staghorn and the other is thread) point to a nutrient imbalance, it brings back memories of the early stages of my 125G. I think once I scaled back on my obsessive replanting, had a steady fert and water change schedule, and removed affected areas things started to turn for the better. If for sure overdosed my micros by a lot at that time.

Break down your current routine, as applied within the last two weeks, for ferts and water change please. If you have test kits, measure whatever you can and post that as well (if you have data to compare from the last two weeks, add them too).

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Yes, it's very likely a nutrient imbalance. I just started fertilizing last week (the algae has been around, in varying quantities, for a long time). Some of the plants have much less thread algae on them, though it is still presents on a few plants and the glass.

I've been waiting for someone to tell me to trim leaves.. The big sword is such a nice, healthy plant. I hate to do that to it. I can get rid of a few of the worst ones but I think all of its leave have the algae to some degree so that won't solve the problem. The driftwood I can remove and scrub on a bit though it has java fern on it that I will have to be careful of. Should I clean the back glass? I've left it alone for the otos purposes. If I scrub off the fuzz algae on it won't it just drift around and attach somewhere else?

For water changes...the last few weeks I've been fighting with the algae water so I was doing changes of about 15 gallons every other day. When I started fertilizing last Thursday I quit that, planning to do the 50% weekly EI water change.

For tests...the only nutrient I have a test for is Nitrate. I just got the kit 3 weeks ago (I think) and every test I've done has read zero. I know I'm doing it right because there is measurable nitrate in my other tanks. Just did a test today and it is still not measurable so I am upping my KNO3 dosage.
Regular params (Ammonia, NO2) have been steady at 0 for a long time. The pH fluctuates by a few points but is almost always 7.6-7.8.

For ferts... Flourish 2x week. 1/8 tsp K2SO4 3X. KNO3 daily in liquid form. I have it set up to give me about 1 ppm/dose so as not to stress the fish by raiseing the nitrates suddendly from 0-10 etc.. I'm doubling the dose for this week to see if I can get a reading.. I think it's better to be safe than sorry but should I be more aggressive with this fert? Also, how will I know if I'm over/under dosing a particular fert?

The tank is by no means taken over by the algae. It is noticable only by close inspecation. But I do not want it to spread and thrive and I really don't like it on my leaves. The plants are all growing. Nothing extraordinary but they all look healthy. I suppose I should just keep up on my ferts and stick to the 1x week water change. Also, I have no more rearranging planned in the near future. The hygro will be slowly phased out but that won't be very tramatic to the tank.

I finally got a reading on nitrate! After doubling the dose yesterday and today it is now reading about 5 ppm. Once I have it fairly stable I may switch to the dry EI dosing a few times/week.

The plants look good. After the last week or so of pulling off dead or snail munched leaves, the hygro is finally starting to take off. All the plants are much cleaner than they've been in the past, except the big sword.

On the CO2 front, my pH is finally coming down a touch but after doing the kH/pH to CO2 conversion it is aparent that there is still not nearly enough in there. The two bottles are producing plenty of bubbles...I think I just need a more effective means to get the gas dissolved. Also, my HOB is not helping. A nice canister filter will probably be my next big investment in the tank but I can't justify it for a while, the Emperor is brand new and cleans the water fine. Is there any way I can modify it to make less surface disturbance?

Also! I've added another 40 watt bulb to the tank so now my total wattage is 144 = 2.6 wpg. I also finally got a timer for the lights. I am well aware that I leave the lights on too long and I've needed something for when I'm gone on weekends. Now my plants should be happy.

lioness,

Glad to read that things seem to stabilize

I would be a little careful on the light as 2.6wpg (of a good light and reflector) can bring you in the zone of "the plants want more". Do you have all these lights on all the time or is there a plan to have a "midday burst" ?

Filling a tank really high so that the outflow of the HOB is partially in the water usually helps a little with lowering the agitation.

And sure thing, a canister would be nice

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

The 40s didn't work out so I'm going with some different bulbs. It is now to be more like 2.3 wpg. The bulbs are all 6500k. Half are on 12 hours/day. The other half will be a little less, probably more like 8 hours.

While prospecting this weekend I took the opportunity to do some rock collecting. I'm considering replacing the driftwood in the center with a rock structure as I'd really like to see more hardscape. The only plant that might have to be moved for this project is the water sprite. Anyway, the river has a lot of iron in it (aptly named Red River) so a lot of the rocks I got are very red. I love the color and want to use them but will it leach too much iron into the water? Is that going to cause another algae bloom or can the plants handle it? I also got a lot of quartz and a few other types of rock so I can skip the iron rich stuff if I have to. I will boil everything and test for pH altering before putting anything in.

I love the color and want to use them but will it leach too much iron into the water?

Yeah, I would not use them. iron is one of your micro ferts and used in tiny quantities (target is 0.1ppm, if I remember that right). Leaching iron would for sure cause problems, IMHO.

I also got a lot of quartz ...

As in black and white quartz or something like that? This would be perfect

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Yeah, I would not use them. iron is one of your micro ferts and used in tiny quantities (target is 0.1ppm, if I remember that right). Leaching iron would for sure cause problems, IMHO.

Now whats the difference between having some rocks with iron in them and products like Flourite?

55G Planted tank thread
19G Container Pond
[IMG]http://i4.photobucket.com/albums/y118/Wingsdlc/Ric

While researching the subject I found conflicting opinions. Here is one take...

Heavy metals (lead, zinc, copper, cadmium, etc etc and even iron) are toxic for fish, inverts, and mammals, including us, when they reach certain-enormously varying-concentrations. In the case of fish, such metals are primarily dangerous in their free ionic form in the water where they are available for uptake by the fish metabolism.

In the form of compounds, such as oxides, they are inert and not free for metabolic uptake. For example water conditioners which 'detoxify' heavy metals actually bind them into compounds which cannot be absorbed by the fish

In water of neutral or alkaline pH heavy metals normally remain locked into such compounds and remain inert.

Acidic water (pH less than 7) on the other hand activates these metals and renders them potentially dangerous.

Iron, the commonest of all metals, is normally present in nature in the form if iron oxide, i.e. rust. It follows that if you have rocks containing iron, betrayed by rusty streaks and patches, it will not normally present a chemical problem for your fish since the rust, iron oxide, is inert, However, if there is enough rusty material it will discolor your water, so rocks that are heavily 'rusted' should not be used. A few patches or spots of rust here and there on rocks is not a problem.

I'm not really worried about the fish. Many natural habitats are very high in iron. Algae is more my concern. I only used a few of the reddish rocks and anything that bleed rust onto my hands was definetly discarded. Now the overall effect is very light, with a lot of white quartz and some other quartz like and granite like rocks of various grey and red shades... (I'm no geologist.. ). Combined with my light sand, it is much too pale and the bright white quartz draws a lot of attention to itself. I want to get some plants growing around and over the rocks to help tone them down. They take up a lot of real estate, which I am not concerned about because I don't have enough plants to fill it all up anyway.

Hi,
Fluorite, a product of SeaChem is actually Laterite,
an ancient (millions of years old) clay. It is formed in
the tropical (Equatorial) jungles and is rich in iron.
The clay is mined, mixed with water, and then baked
(fractionated) into brick like consistency. Then the stuff
is ground up into #2 & #3 grain size for use as aquarium
substrate.
Unlike some other "plant friendly" substrates, the Fluorite
does not loose its iron over a period of time.

Clays particles range in size from 0.00006 to 0.0020mm
and the minerals that make up clays are mostly
silicates of aluminum, iron, and magnesium. A variety of
clay called Vermiculite has a general formula of:
Mg.3[(Mg2.3Al.2Fe3+.5)(Si2.7Al1.3)O10(OH)2]-.5. nH2O
Note the OH Radical, and the H20 molecules. This is easily
broken down by plants to extract the Magnesium, and Iron in
the clay.
The iron molecules in minerals or rock is more
tightly bound, not organically bound and not accessible
by plants. In essence, as the article says, its "inert."

Iron, in minerals, or even in the water, depending on its
form, can stain the quartz gravel that we use.
If the concentration is high enough, its action would look
much like iron rich well water on white porcelain sinks.


Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

An update....

I have good news and bad news.

Good:

Plants are all doing so well! Growth is very impressive as compared to previous no ferts/co2 situation. Ludwigia is a nice rosy pink/green on top and bright red on bottom. Vals are looking gorgeous at long last and are sending out runners (finally!). Dwarf sag is also sending out runners for the first time. There is lots of very nice new growth on wisteria, water sprite, and all swords. Plants are actually pearling at times! I didn't think they would do that at lower CO2 levels but I get little bubbles on the bleheri sword and water sprite. While I am updating plants... I added a marble queen sword(had one baby when I bought it and is working on its second one now) and more ludwigia and removed all the hygro.

Bad:

Ugg... More algae... I have new varieties too. A dark brown (BBA?) algae is present on the older leaves of wisteria, swords, and water sprite. Mostly along the edges. My poor anubias nana has finally been attacked and is now being covered by the brown and green algae. There is still plenty of fuzz algae, on the swords mostly and also a little on the glass. I've been cutting off lots of sword leaves as they become covered but I don't think it is helpful. The worst news... I believe I have spotted BGA. Saw some tiny spots on a few leaves and on the gravel in a small patch at the front of the tank. Upon further inspection, found similar looking algae on the glass all along the front under the substrate. I removed the few leaves and any sand or decor that had it. It is a bright green, slightly blueish slime. There was very little but it seems to indicate more to come. No green water at the moment. I suppose the new algae could be the result of adding the rocks. I did boil and scrub them all thoroughly. Only one piece had visible algae and it was subjected to a bleach soak and extra scrubbing. I thought that would be sufficient but perhaps not?

What am I doing wrong?! I am so sad and frustrated. I feel helpless as I have been trying hard and I really don't know what the next step to take is. I dread a tank crash.. I have been fertilizing regularly with K, Flourish, and enough KNO3 to keep the Nitrates around 10 ppm. Approx 50% water change and light surface gravel vac once a week. 2.3 wpg 12 hrs per day.

The only things I can think of are high phosphates or perhaps insufficient circulation (though algae is present throughout the whole tank, not just the low circ side). Would a phosphate remover be a worthwhile try? A phosphate test at least? What should the phosphate number be? The water is pretty warm too. About 78, which is room temp (the heater is set at 72 and never kicks on anymore). Could that be contributing to anything?

My poor tank. It looks so pretty. I really don't want to lose it. I've been longing for this setup for years and really wanted to do it right. This is my first try at a big tank, I've only had 10 gals before. Never in my 10 years of fish hobbying have I had so much trouble with algae (though admittedly, my old tanks were much lower tech and few had live plants). This is discouraging.


As a side note, I have another tank going at the moment. It is a 10 gal, low tech, no ferts/co2, heavy fish load, well planted. Growth is moderate, all plants healthy. There is not a speck of algae visible, nor has there ever been in the few months since I started it. Maybe a 55 is too big for me...

Lioness, don't get down on yourself . We all have algae at one time or another . The trick it seems is to get balance in your particular environment.
Not easy , trust me I'm having lots of issues in both my tanks at the minute . I'm just trying to see it as a learning experience .
Thats part of the fun and challenge .

Persevere , and when you win you will feel a greater sense of achievement. Enough of the pep talk .

I would go to the Seachem site and have a read about ferts .
I would certainly get a bunch of test kits and try to find out whats going on , but thats me, others will say just go with the EI method and make sure all your Macro's etc are there in excess .
From my reading it will probably be something missing rather than an excess of something thats letting the algae outcompete the plants .

Hope this helps , stiff upper lip (as the Poms say ) and you will win in the end .


Garry

Thank you for the encouragement Garry.

I have been roughly following the EI method. I'm going to cut down on my Flourish just a touch and I'm also going to get a Phosphate test kit today.

If any of you read my post in the Hospital, my fish are now infested with leeches. Such joy....

Pictures of various things to come.

Here is one of my poor infested Pearls in the hospital tank...

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Some nice new leaves on the red melon sword. Note the nasty algae coming up on the older leaves.

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Water sprite. One of my favorite and fastest growing plants. The new growth is so beautiful on it, but you can see the ugly brown parts of the plant. Not rotten leaves, just algae.

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Was called Rosette Sword by the LFS. Very nice plant. You can see all the stumps at the bottom where I have been cutting off the worst algae leaves. All my swords look like that now. Also note that the leaves are ruffled. I don't recall them being that way when I first bought it. Water issue maybe?

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A baby val! (off center right) You can see the runner coming from the plant on the left. The vals are finally free of the hair algae they had and they are all growing so nicely now but some of them are getting the brown algae...

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Ludwigia. The original pieces I had were just existing, not growing. I added four more bunches after I started fertilizing and all is doing well now. They appreciate the extra light too. Also, my narrow luds are finally putting out some new leaves.

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Anubias. This plant had been doing really well for the longest time and now look at it. I finally broke down and removed my first leaf from it. It is really coated with a thick, dense algae on some leaves.

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One more of the water spirte. The new leaves are so soft and bright. I love this plants, it is a great grower.

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Your water quality has to be really bad for your fish to be sick and your plants and tank to be coated with algae. Why do you think this is so?

My Scapes

I don't think my water is bad at all. I don't ever neglect my tank. I feed moderately. I do a water change faithfully every week. I have no sick fish and no deaths. They simply picked up a parasite, probably from some new plants.

Here are full current params to set your mind at ease:

Amm: 0
Nitrite: 0
Nitrate: 8
pH: 7.4
kH: 5
Phosphate: .25

I think the suggested P measure is .5-1 ppm. So does this mean I actually need to add P? I'm suprised. I guess I'm going to be in need of an enema then. Can anyone tell me how to dose the tank with the Fleets?

Edit:
Saw on a different forum a reccomendation of 3 drops Fleet after water change, check at midweek, then add more if necessary. Does that sound ok?

I don't think my water is bad at all. I don't ever neglect my tank. I feed moderately. I do a water change faithfully every week. I have no sick fish and no deaths. They simply picked up a parasite, probably from some new plants.

First off, most test kits are crap. They simply don't work. If you have lots of algae issues and infected fish you have something wrong with your water. First thing I would do is siphon out all of the sand on top of your gravel. That's preventing the bacteria on the gravel from getting enough oxygen so they are dying off and releasing waste into the water column. You are going to continue to have issues if you don't remove the top layer of sand.

My Scapes

Lioness:

how are tank and fish? You haven't posted for a while, are the gouramis free of parasites by now?

hope everything is fine

Lioness , how are you doing. Everything all right? .
Lets us know how things are in your tank .

Garry

Well, I've no idea how the 55 is doing right now as it is in the middle of a blackout treatment for algae and is covered with a blanket. I did my regular 50% water change before starting it but didn't add any ferts. So no light/co2/ferts/fish food for most of this week. I hope everything comes out ok.

As much as I didn't want to, I did make an attempt at removing the sand. It quickly became apparent that that simply will not happen without completely tearing down the tank and starting over (which may eventually happen anyway). My substrate is over half sand so all the plants would be uprooted plus some flourite is mixed into the sand which means removing some good substrate too. The sand stays for now. I did add some MTS hoping they will help keep the substrate from compacting.

All three pearl gouramis and one oto were removed to a ten gallon hospital tank for treatment for leeches. Tried a strong salt dip first. No luck. Had trouble finding a parasite med locally so LFS recommended trying Furazone-light. No luck. Lost one female pearl. Had a word with the management and was given some Clout. Several leeches detached, though they didn't actually die, even after two treatments. Ended up removing the rest manually. The oto is currently in another fully planted 10 gal and the two pearls will stay in the hospital until the blackout is over. The color on the pearls is amazing and the male is building a cool little bubble nest in the corner. I think he's getting ideas. At least I know they've made a full recovery.

I did find out exactly how I got the leeches in the first place. Found the same critter on fish in the 150 gal plant sale tank at the LFS and pointed them out to the help. I was disappointed. This is usually such a great store! They are taking care of it now at least.

Will update on the main tank when the blanket comes off. Thanks for the concern Garry and catdancer!

Lioness,

don't dispair! The algae outbreak will pass, algae are a part of our lives, they are everywhere. Glad to hear that you figured out the source of parasites, they had to come as hitchhikers. Unfortunately, even the best stores are not immune to them and other bugs and the possibilities to acquire them are endless,espeically with new livestock arriving permanently.

I just changed the substrate in my tank from gravel with laterite to Eco Complete. It can be done rather quickly and my tank is up and running again!

Catdancer, could you offer any advice on the substrate changeover? It seems rather daunting. I sure liked the sand... It was for my cories, who now have the longest most beautiful wiskers. It does look a bit dirty though, especially when it settles on leaves.

Turned the tank lights back on this morning. It looks a lot better and all plants made it through just fine, except a bronze crypt which melted into oblivion. I think the vals actually added another couple inches and I've got lots of dwarf sag runners. The leaves which had the heaviest algae infestations (swords, sag, anubias, and wisteria) are mostly clear. Some still have some algae on the edges. I will probably trim most of that out. No more blue green algae to be seen! Checked all params and everything is fine. I have another big water change planned for today then fresh ferts and co2 again.

lioness,

Glad to read that most issues seems to have been corrected with the blackout, but keep in mind that if you don't correct the sources of the issues then they will come back.

If catdancer suggest that you change your substrate with fish and plants in the tank then I will say "I wouldn't do that" . It worked for her, but it is to risky for me, in particular because your tank is very sensitive now with regards to messing around after a blackout.

Keep us posted and add some pictures of the tank now.

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

If catdancer suggest that you change your substrate with fish and plants in the tank then I will say "I wouldn't do that"

Hey! Where did I suggest that? No hopping to wrong conclusions, please
What I meant is: change of gravel can be done rather quickly w/o implying to keep everything alive inside!

I am not convinced that lioness' problems had anything to do with the sand in the first place (BTW, the Eco is surprisingy fine in grain and can give rise to 'dust' as well)

I am not convinced that lioness' problems had anything to do with the sand in the first place (BTW, the Eco is surprisingy fine in grain and can give rise to 'dust' as well)

Ever hear of the word suffocation. Nothing is definite, but putting a thick layer of fine sand on top of a gravel bed of nitrifying bacteria will deprive them of oxygen that is brought to them through water movement the same way the filter flow provides the bacteria in your filter with oxygen. That being said, the biofilter (that is mostly in the tank) will be limited and not be able to consume waste, etc. that will lead to additional algae problems.

I don't know how you went about removing the sand, but I can tell you an easy way that will create no dust and will actually clean your tank at the same time.


My Scapes

lioness , So pleased to hear that you appear to have solved your problems with the Parasites on the fish.
Sorry to hear that you lost a Pearl though
Glad the blackout worked for you . Remember though you will always have some algae!!!!
You need some food for the Otto

I would agree with Ingo on trying to work out the cause or it might just return as before .
If there is anything any of us can do to help just let us know .

As far as removing the sand , I'm not sure why you want to do that . You've got it over Flourite so that should be good for your plants .
Whats the issue ?
I've got to say I would be reluctant to do it myself .

Anyway lots of good news , so be happy and enjoy .
Garry

Here's a nice little update for you all.

The tank is doing very well at the moment. I finally got some P in the tank, it is sitting at 1.0 at the moment. Nitrate is 10. Last week I removed the anubias, the bleheri sword, and one marble queen sword and gave them a bleach dip as they all had ridiculously tough algae on them. The anubias came through perfect and clean but I got distracted and accidently left the swords in for 10 minutes! They became perfectly clear bleach plants. I replanted the root balls anyway and already have nice new leaves coming up so the plants are definetly pulling through. I have been on a trip the last three days and as I only have one of my lights on a timer, the tank only got half strength lighting while I was gone (just over 1 wpg). Some of the plants look a bit paler but almost all of the nasty algae is gone. There is plenty of green spot type on the glass but that is to be expected and is easy enough to deal with. The tank looks very nice. All plants are healthy and thriving. The smaller swords in particular (red melon, oriental, and rosette) are looking incredible and are sending out lots of new leaves. In my absence the water sprite hit the top of the tank! Yay! Finally a tall plant! I've been despairing that I would never get anything to grow taller than half the tank. There has been some slight change in decor. The bleheri sword was moved for the first time since the begining of the tank when I took it out to bleach it. I planted new baby water sprites all along the back in the sword's old spot and moved the sword farther forward and to the right.

I'm very pleased with how the tank is doing right now. The right side looks very bare because the new water sprite is so short but once that grows in it should be pretty nice. All fish are healthy and beautiful! I hope I can get this to last.

I may dare to post some pics later.

I took a few pics but nothing came out very well except for this one. It is a new baby cory cat. Note the happy sword plants he is sitting among. I lost one adult cory during a heater malfunction and so have added three little ones to boost my herd to 8. They are doing great and schooling happily with the big cories, which look like absolute monsters next to them! I love cories...

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nice photo! good to hear your happy with your tank

lioness, Fantastic news , I'm so glad its all going well .
The shot of the Cory shows up the nice healthy sword indeed .
Well done .

Garry

Lioness, this is great!

The leaves look extremely healthy and the little Cory very happy. BTW, what type of cories are you keeping and at which temperature? I am having very bad luck with my cories (out of 7 only one is left!).

I would also like to know lioness. I have only 3 Panda Cories left out of like 10. I would like to try a different species of cory.

Thanks for your input as always, Shane
http://thetanklog.blogspot.com/ - [ Thanks to ScottF ]
http://www.natureaquariumclubofutah.com/main.html

Sorry to hear about your cories... I am by no means the cory expert around here but here are a few ideas.

Mine are Paleatus (common pepper variety) and the tank stays ambiently around 78-80. This is on the high end for a cory but I can't keep the tank any cooler without a chiller during this summer heat. Too much heat is hard on cories, I think I read somewhere that it damages their slime coat. My tank was over 90 when a cory kicked the bucket and I had been gone a few days so have no idea how long it was like that.

Being bottom sifters, cories are the first to be affected by any mulm building up or other nasties in the substrate. Some species of cory are very delicate about this. Pandas are notorious. They need very regular gravel vacs. Another problem with being a bottom sifter is food. Are they getting enough? Sometimes just leftovers are not sufficient. Also, what kind of substrate do you have? Sharp gravel will tear up their whiskers, it could run their systems down and make them sick. Don't know if that in itself is enough to kill them.

So far my experience with my cories is that they are very tolerant of water chemistry. They were the first fish in the tank and have thrived since day one.

I'm sorry you are having bad luck! Any ideas what could be wrong?

Lioness

Also, what kind of substrate do you have? Sharp gravel will tear up their whiskers, it could run their systems down and make them sick. Don't know if that in itself is enough to kill them.

I have peasized gravel in the aquarium. It is not sharp at all and i have some smooth larger rocks, i have some slate and i have some Petrified wood also, none seem to damage the cories.

Being bottom sifters, cories are the first to be affected by any mulm building up or other nasties in the substrate. Some species of cory are very delicate about this. Pandas are notorious. They need very regular gravel vacs. Another problem with being a bottom sifter is food. Are they getting enough? Sometimes just leftovers are not sufficient.

I Add Alage wafers every other day and my omother in law adds the odd piece of Zukini now and then also. I also add frozen brine shrimp every now and then as a treat.

I have also added an extra tube to my intake so that its at the bottom of the tank. I gravel vac 1/4 of the tank each week.

Thanks for your input as always, Shane
http://thetanklog.blogspot.com/ - [ Thanks to ScottF ]
http://www.natureaquariumclubofutah.com/main.html

There are so many variables that could be causing your problem. Maybe something as simple as a weak batch of fish. Or they could have been carrying a disease. You need to think about things such as: how soon after purchase did they die? Did all die at once or was it gradual? Are other species affected? What symptoms did they display prior to death? Were any other factors changed around the time of death? New fish/filter change/new decor/etc...

I'm sorry but this is a bit off topic and I don't have all the answers for you. Try a post with all this information in the Hospital or maybe the Bottom Feeders board. Your questions will get a lot more attention there. I hope your remaining cories are doing good, don't give up!