OK, I have a problem....?

Question

...with my aquarium. I have had 6 zebra danios and 3 marble mollies in it for about 8 weeks, all was going well... until recently. They started hanging at the top of the tank all the time, and then slowly, some of the danios were swimming on their sides and upside down etc. - I belive this was a bladder infection. I lost 3 of the danios. I gave the tank a good clean last week, and a 40% water change - and I have since lost ALL of my fish...!
The mollies and 2 of the danios seemed to be dead - but at the BOTTOM of the tank - when I went to get them out, they were actually still alive, but only just. Why were they sinking, not floating??
I have a small amount of brown algae on the rocks/glass - so I was thinking of getting an Oto to get that sorted, but I am worried that the water my be 'polluted' from all the sick fish...
My question is, now I have an empty tank again, shall I do a partial water change before I add any more fish, or should I start over and clean/change it all??

Answer 1

I think cat has the better answer here then the rest. You know cycling your tank out is a real bear so before we go through all that part lets examine the other possibilities. However, if your tank is empty now, and has been for quite awhile, you're already at day 0 then. Without a constant source of ammonia and nitrite to oxydize, your bacteria is going to die off. So depending on how long your tank has been empty again we may well be going through another cycle. That's neither here nor there in terms of what caused this though.

So now let's take a look at that. If you didn't test the water chemistry can't do much about that either. Danios and Mollies are fairly hardy fish in terms of coping with the cycle so at 8 weeks in, if it was a matter of ammonia poisoning as the fish being on the top of the water, that would be an indicator it was that, it would have occured sooner then 8 weeks. I am thinking that it might be long term exposure to nitrites though. The water change should have eliminated all the factors in terms of that however. 40% change would really get the levels down. PH may have been a factor but I rule that out becuase of the length of time. Had your PH been out of range, I feel you would have seen signs of that within 10-14 days. If you did not add anything to radically adjust the PH then I think that takes PH out of the question.

This doesn't mean it couldn't be ammonia nitrite or ph, but odds are it's not that given the information present. I would think looking at the syptoms and actions of your fish, it would sound like a pathogen made it's way in there and I have been informed by MM as my Arowana died of Costia two days ago, some pathogens can be present in the water from the start and take some time to grow or thrive to a point where a fish might become afflicted. So getting your water tested PRIOR to emptying that tank I'd think is a must. I would consult with MM here and maybe a full spectrum antibiotic dosage or medication to treat a broad range of afflictions might be needed. Also run a test on your tap water and see what the natural condtions are. Even with treating for Choloramine and Chlorine there maybe trace elements or a contamination that is not harmless to human life but to fish in the water supply. I don't feel this is likely but we are trying to rule out as much as we can. Getting your tap water tested will help.

Please keep us up to date in your results.

JV

On a side note for cat, your Nitrate levels are generally not needing attention until you get to around 40 ppm on that, not 25. At 25 it's still considered to be in the safe range.

Answer 2

you don't say what your tank maintenance schedule was. i would test the water before adding anything else. if the fish were showing no other symptoms other than being dead, it could well be an imbalance in the water that killed them. i would invest in a water test kit rather than take water to a shop to do it (sometimes they can bend the truth a little to get you to buy something else). The API Master test kit I recommend, it's worth the investment! Your ammonia must be at 0, your nitrites must be at 0, your nitrates under 25ppm. There are several other different things to test for, but those three initial ones will let you know if your tank is healthy or not. If you find you do have levels that are a little off, do another water change, and test the water the next day (it's not good to test it straight after a water change).

if you find it is all normal, then it could have been an infection that took your fish, in which case, seeing it did take them out so quickly, a tear down, scrub, and redo of the tank may be in order. and re-cycle the tank once done before adding new fish. (see link below)

fish don't float when they're dead unless they've been dead a while.

with otos, 8 weeks is still a little new to be adding them. they really need a matured planted algae-infested tank to thrive, to be kept in a trio or more. they can be sensitive to water conditions.

Answer 3

This is a tough question to answer because it could be many things. Do the fish have any marks on them? If so it could be a parasite. Even with a large water change parasites do not die they manifest in the gravel. Also your water may be tainted so the question is what type of filtration are you using? Again there are many questions but I agree with the responses about a total clean out however when you do that you will kill your good bacteria bed and you will have to start all over. Good luck....

Answer 4

your best bet would be to empty the tank and clean it out then put fresh water in then get some different kits to check the ph levels and other things you will be better of going to your local pet store like pets at home and ask them what you will need has they are really helpful then wait a few weeks and keep doing the tests than slowly had your fish if you do not do it properly all you are going to do is waist money on buying fish
hope this helps

Answer 5

If you take a small water sample to your local pet shop or the shop where you brought the fish from, they will be able to do a test to see if you have the right balance in your water. This could be whats killing your fish. Have you got any oxygen (water and air pumps) in your tank? If they haven't got enough air then they will also die.

Answer 6

I agree wiht PETER m. I think you should clean out everything. The next tank you should have should ne first housed in an OTOCINCLUS to start the cycling and to eat some of the algae. I would buy another tank.

THe reason that your fish were at the bottom is because they had no more energy to use to swim about,.

Answer 7

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Answer 8

Yes i would say that you have an infection in your tank. You need to to get it sorted before you put any more fish in. You can get info from google and also fish FAQs like www.aquariumfish.net/home.htm (copy & paste this) or aquariumpros.com. These websites have all the info you will need on what to do.

Answer 9

I would completely clean it out and start over again.