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Help!

I came home from work to find three dead pentazona barbs in one of my tanks this evening. I have no idea why. I'll try to mention everything that seems even remotely relevant, and perhaps someone can suggest what may have happened, and what I could do to help matters, as some other fish seem unhappy too.

I did a 20% water change on both my tanks on Saturday, cleaned the filters and replaced two out of four filter sponges in each tank, as they were all quite old and clogged, and due for replacement. (I took care to preserve the friendly bacteria, and rinsed the new sponges in the old water before replacing them - all the usual stuff that I have done many times before)

The affected tank has 11 pentazona barbs, some corys, some rainbows, an Albert's catfish and far too many bristlenoses. I have had 5 of the barbs for about 3 years and the others I only have had for a few weeks. Apart from the newer barbs (replacements for a few bristlenoses I managed to catch and sell to my LFS, so they represent a net loss of fish inches, if anything) the tank has been in its present form with exactly the same fish for at least a year, and been fine.

All the dead fish were the older barbs. Albert seems listless, as do the remaining other older barbs (but the new ones are swimming around reasonably happily) Most significantly, all the bristlenoses are clustered around the air line, which almost certainly means something is wrong. But what? No fish are gasping at the surface, or showing signs of needing more oxygen, except for the bristlenoses.

I immediately tested the water, expecting to find sky high ammonia and even had the ammo-lock ready (reserved for dire emergencies only). But, no, ammonia and nitrites are both reading absolutely zero. I have two filters in this tank and both are working fine, so I haven't done something dumb like forgetting to turn one on again after cleaning (has been known)

I've tried to think of any contaminant that may have been introduced into the tank by mistake, and can't think of any way that anything undesirable could have got in.

I also took a look at the tank temperature (as I have been known to boil fish by mistake, in my early days of fishkeeping) It is showing 80 degrees, which is normal for that tank at this time of year.

So I can only suspect some sort of disease, but what? If the newest barbs had inroduced it, then why are they fine while the older barbs died? Why has it only hit the barbs? Why are the Bristlenoses gathered around the air line?

I just took another look at the tank, and another older barb is in its final death throws: he is struggling to swim upright, and is mainly on his side or upside down. But his colour is good and he has no growths or marks on him.

I'm going to put a little aquarium salt in the water, as that's all I can think of to do. It may help, and probably won't make things worse.

But has anyone got any better suggestions?

what size tank?

but also what stood out is the addition of the new barbs. prehaps illness from them.

Could you check your nitrAte readings?
In your normal routine how often do you do water changes?
If there much water surface agitation? If not there could be low oxygen.

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Before you criticize someone walk a mile in their shoes. That way you're a mile away and you have their shoes.

Maybe new members to the school stressed the old ones out? It the younger additions establishing the new peeking order. Have you observed their behavior at all?

20 Gallon Long:
Aquaclear 300
2 Bolivian Rams, Mikrogeophagus altispinosus: Gumby and Pokey

hi,

I'm really sorry about not getting back sooner, and thanks for all the prompt replies.

I still have big problems (fish dying daily) and I still have no idea what the problem is, so I'll answer your questions and tell you what else has happened since.

I don't think the new fish were stressing the old, as they are all tiny (aorund 1/2 inch) and the next smallest fish (the older barbs) are about three times the size (or were, to be more accurate, all dead now :-( ) Anyway, they all used to swim in one big shoal, until about two days before the old ones started dying, when they began to swim in two separate shoals (may be significant)

The tank is twenty gallons. It is badly overstocked, because the bristlenoses keep breeding, and they are really hard to catch. But it has been like that for at least two years, although of course, the bristlenoses have been steadily growing (and breeding) all this time. I regularly catch as many as I can and take them to my LFS (but that's obviously not enough as when they all come out looking for oxygen, I counted 15!! between 2 and 6 inches in length) To help overcome this I run the tank with twice the filtration and three oxygen lines, and have done for a long time. I do regular water changes (every fortnight at least) and monitor the water regularly. The tank has been stable for a long time now in this configuration. The 6 timy barbs I added were more than compensated for by the bristlenoses I took out a few weeks before.

The day after my post, I took a careful look at the most lethargic barbs, and saw whitespot (which wasn't visible the previous day) So I started the whitespot treatment (Protozin). The following day I did another water test, as I couldn't believe there wasn't a water problem because of the way the Bristlenoses were behaving. The readings were Ammonia 0.5 (previously 0), Nitrite 0.25 (also previously 0) and Nitrate 5ppm [I don't normally worry about the nitrate levels too much as (i) my tap water usually tests at 40 ppm (ii) by the time the nitrates are high, something will be very obviously wrong]

Some of the bristlenoses seemed to have rather bloated bellies, which were be a whitish-yellow colour, rather than the browny-pink of well fed healthy bristlenoses. One or two had a few white spots too. Some of the smaller barbs were also showing signs of whitespot.

I did a 30% water change (and replaced the correct amount of whitespot treatment), as I figured that could only help.

That was Saturday. I have now lost all but three barbs, and about 6 bristlenoses, including a beautiful (and ugly) 6 inch male . The remaining barbs all have whitespot, and I am not hopeful that they will survive much longer. Albert seems listless, but that may be because I've been fishing around in the tank rather a lot recently, and he finds that a bit disruptive, and often seems to "play dead" when he feels threatened, rather than rushing off to hide. Several of the bristlenoses are not happy either. The good news is that the corys and the rainbows all seem fine so far.

I did another water test today. I now have ammonia 0.5 (as on friday) / nitrite 0.5 (up from 0.25) and nitrate 5ppm (as before). But that is after 3 days of protozin treatment.

So I'm flummoxed. Other than continuing to treat for whitespot, and keeping an eye on the worsening water, with the amo-lock to hand, and waiting for the rest of my fish to die, I can't see what else I can do.

Any suggestions?

To be a bit more upbeat, my other tank is fine. I have three beautiful clown loaches, and several other happy healthy fish. I just needed to say that! I'm trying not to think too much about the tank of death in my dining room.

The nitrite and ammonia really need to be zero, ive used protozin plenty of times and never noticed adverse water chemistry because of it, I think your fish are simply succumbing to the effects of nitrite ,ammonia and nitrate,and the lack of disease resistance that brings.

The nitrate reading in this case could be a problem. 40 ppm is as high as many keepers will ever let their levels get, and if it comes out the tap like that you have to find a way to get it down.I dont see how the tank reads 5ppm and the tapwater reads 40ppm unless you use denitrifying aids, or the test kit is off. I'd be tempted to do yet another water change, your changes will need to be at least weekly, and perhaps around the 30% mark and you really do need to net the excess fish and pass them on asap, or start another tank. It sounds like your tank is crashing, and only thorough gravel cleaning, water changes and lessening the stock will save it. Classic case of leaving the upscaling too late.

Thanks everyone for the advice. I think I may have turned the corner. I had a brainwave at midnight last night and got out of bed to add yet another air line. I had been reading Kathy Jinkings' excellent Bristlenose book again, in desparation, looking for help. She says "Bristlenoses are tough and hardy fish and diseases and disorders are fortunately rare ... [they] will be one of the first fish to show stress if the oxygen level drops" That I know, but then she goes on to talk about fry tanks, which I didn't have, but I did have (had) far too many adults. "Be prepared for their growth rate, the tank can go from 'plenty of room' to 'dramatically and fatally overstocked almost overnight' " she says.

I think that is exactly what happened. One day the tank was fine, the next they all grew a bit more and it wasn't. Hence distressed bristlenoses and also an opening for whitespot to attack too.

This morning I came downstairs to find some of my remaining bristlenoses on the rocks and bogwood rather than all round the airlines gasping for air. Only one has a yellow belly, the rest look healthy again. I had two more dead barbs, but I think that was inevitable due to the whitespot, and they were not looking good last night. I'm just so sad that 6 beautiful bristlenoses had to die (and 9 barbs) before I realised this simple explanation.

Like you, "longhairedgit", I suspected water quality problems and was surprised at the low readings (0.0s at the start of the problems, now rising slowly, hence another water change). I know 0.0s are better, and I'm sure I will get back there soon. But I now think the initial problem was lack of oxygen, which had a knock on effect. Unfortunately, I thought the brsitlenoses' distress at the lack of oxygen was a symptom of another underlying problem, rather than the cause. I thought the initial deaths were from the root cause, and was looking for that to deal with, but I think those were a consequence, not the cause.

I've certainly learnt a lesson which i hope will be useful in the future.

As an aside, I was really surprised about my low (for me) nitrate readings. As I say, I don't normally bother to test it as it is always so high because of the levels in the tap water. So a reading of 5 is really really low for me (60 is more normal, even with 0 ammonia and nitrites!!!). Either the water company has reduced the base levels in the mains water, or my tank cycling is so efficient that it eliminates both the fish-generated waste and the water company-generated waste.

thanks again. I'll let you know what happens.

You are to be congratulated for coming on in your skills, however , I think you'll find that the filtration will not be responsible for the lowering of nitrate, it can be done with the addition of certain bacterial cultures, or absorbed into resin designed for the purpose, but a filter actually produces nitrate, it is the final change of properties for ammonia, and the final form of ammonia, you simply have to ditch it. Plants will not make a significant impact on nitrate in a heavily overstocked tank either.Odds on when you have high nitrate in the tap and not in the tank, the test kit is off, or there is an additive in the water that makes the test kit give misreadings.