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Hi, I'm hoping someone might have some ideas about why I'm losing my Rasboras. They are about 1.5 years old. The tank is as follows:

20 Gallon tank (sorry I don't know how many litres that is) with:

2 Serpae Tetras, 6 small Silver Dollar Tetras, 1 Pleco, 4 Blue Rams and now 2 Harlequin Rasboras (used to be 6) and 1 Otto Cat and some live plants.

The water when tested today was Ammonia 0, Nitrite 0, NItrate 20, pH 7.0. I keep the water temp at 78

The fish all appear healthy. I cannot locate anything really wrong with any of them. They appear fine one day and the next day they are dead. All the other fish are fien also as far as I can tell. I have lost four of the Rasboras over about the past approx. five months (about one a month) the final one being today. I am really stumped. THe only thing that is different really is that I have a little more algae than I did about six months ago but nothing extreme really.

well your tank is overstocked- Ive got a hard time understanding how your nitrAtes are so low. how are you testing the water???

silver dollers need a MUCH larger tank

As for the harlies- is their color fading, are they flicking( rubbing against stuff), can you see any abnormalities on them before, or after they die.... all this would help.

Hi, thank you for replying. I think perhaps I've mislead you by calling the fish Silver Dollars....these are small fish not big at all. Maybe they are called something different. I'm just going by what they were called at the aquarium store where I bought them. These fish are not even an inch and a half in size. I don't think my tank is overstocked. Seriously, the fish have all been fine for almost two years. I use a master kit tester set to do the testing and the results have been fairly consistent for the most part since I first introduced the fish to the tank.

As far as I can tell the Rasboras are not acting strange in any way. The only bizarre behaviour I noticed was in one fish that seemed to be not hanging around with the rest of the school of Rasboras. He ended up being one of the ones I lost. He appeared to be hanging off to the side behind a plant before he died. But other than that I really haven't noticed them doing anything out of the ordinary. The don't appear to have unusual markings or any kind of sickness either. I'm really at a loss.

~~ oh sorry I forgot to mention that I have noticed that after they are dead their bodies appear to be slightly bent (if that makes sense) almost like if they were still swimming their tails would be hanging downwards...I wish I had taken a picture now but I didn't really think to. I was rather upset by them dying.

Also, I asked my husband and he says the fish are not called silver dollars they are called Blue Tetras. Does this make more sense in terms of numbers of fish?

have you had a power outage lately??
What is your water change schedule?
Have you done anything /added anything new to the tank lately??

if they are blue tetras- chances are they are dyed white skirt tetras- which is fine in size for that tank.There are blue tetras, but are pretty rare, and need special care.

what kind of pleco?? common, bushynose, or other?

your serpeas- how are they acting? are they nipping other fish, chasing ect??

Hi, Nope I've not added anything new to the tank in ages. The last new thing I put in was probably last summer and that was just a new plant. No power outages either. I change 20-25% of the water every week to week and a half. I have a Penguin filter with bio-wheel. I change the filter pretty much every week or two.

The Tetras could very well be what you describe. They aren't particularly blue. They are quite nice looking though. The pleco, as far as I know, is just a common pleco. He mostly stays on the driftwood I have in there.

The Serpaes largely stay in the bottom area of the tank. They occasionally get into scraps with the Rams and very rarely with one of the Tetras. I've never seen them bothering the Harlequins at all as they usually stay at the top of the tank. The Rams don't bother with the Harlequins either. I'm really stumped on this. I've been watching the remaining two Harlequins to see if I can notice anything strange and I really can't. To me they look normal. No colour change no strange behaviour except of course now there are only two so perhaps they aren't too happy. I'm not sure. Its distressing though.

Their slightly bent-ness could just be rigormortis, though it's helpful to know.

If you've had these fish for a long time now, is it possible that the rasboras are simply dying of old age? If they seem healthy beforehand, this could be the case.

That is what I originally thought (ie. they were dying of old age) but then someone told me they can live upwards of 5 years! These are only 2 at the most. I would be pleased actually to learn that it was old age...maybe I'm being misinformed on how long they live?

Fish life spans are hard too determine, water chemistry/ tempurature/ foods/ how the fish was kept before you got it, ect all play a part, and tehn their is also not kknowing how old the fish is when you get it. Especially at a fish shop that allows trade ins.

Well yes that makes sense. Well maybe I'll go with "they have lived out their life" then. That makes me feel better than "something you did to them killed them"!!! All my other fish seem happy and healthy so perhaps they are just dying of old age.