why do my fish keep dying?

[milknhoney]

My fish are dying off, one by one. The last several fish that died didn't have any outward symptoms other than appearing to be a little more lathargic and reclusive than usual. Then, after a few weeks, they look contorted and then they're gone.

I had a couple of fish die of what I think was popeye. But the last three or four were as described above. I was treating the tank with Paraguard, but that doesn't seem to have made a difference, so I stopped.

I have a 10 gallon tank, currently inhabited by 1 platy (purchased a month or so ago) and 6 black mollies, the only remaining survivors of a bunch born last April. Their mom was one of the popeye victims.

I've been checking the tank parameters. The last time I checked was four days after a PWC, and ammonia was .25, nitrites 0, nitrates around 20, ph around 7.6. I did another water change yesterday at the one week mark - replacing two gallons.

Tank is 10 gallons with undergravel filter/powerhead and a sponge filter.

I think for a while the tank was overcrowded - after the babies were born. But now there are only 7 left in the tank, seems like that problem should be gone. Also I think for a while my daughter was overfeeding them, but that problem seems to have been corrected now too. I was also wondering if big box pet store fish have a shorter lifespan. But it is happening to the babies that were born in the tank too.

Any advice or help?

Thank You!

 

[agrasyuk]

there are so many reasons possible.


but first things first - I would do a water change. since its only a 10 gallon a 50% change is not to hard to do every day or every other day for a week or two.
I really really don't like the undergravel filter. not saying it is the problem (it might be), but I would never use that. my 10 gallon runs perfectly for over two years now on a cheap walmart HOB, which also eliminates the need for air pump. I'm guessing a single sponge will be sufficient for now until the small ones grow enough to not get sucked into HOB

 

[V227]

Keeping stable water parameters in a small tank is difficult at best. Things get even more complex with over crowding and feeding. I think you answered your own question.the noted fish fatalities were likely due to an ammonia spike or a bacterial illness. As you gain experience things will level out and become more enjoyable.

 

[Andy Sager]

2 things that come to mind is that the ammonia level being above 0 is an issue with something in the tank. That should be addressed.
The next is that paraguard is for parasites and the most common causes of Popeye are bacterial in nature and so paraguard wouldn't help that anyway.

For what it's worth, Undergravel filters had their "day in the sun" ( I was using them back in the 60s and 70s) but have been replaced by much more effective filtering systems today. Their biggest downside is that they need to be cleaned out underneath the plate so that the nitrate level, created by the mulm accumulating under the plate, doesn't go crazy. I would consider removing the UG and just keep the sponge filter working and see if that addresses your ammonia issue. You might also want to check your source water to see if that is where the ammonia is coming from. A reading of .25, 4 days after a water change, sounds like the tank has not cycled fully. It is confusing because of the nitrate reading. Unless the source water has nitrates, an uncycled tank should not have both ammonia and nitrates at the same time.

Lastly, yes fish quality is an issue. Not all fish are created equal so their longevity and health can be attributed to where you got them from. As a general rule, cheap fish do not last as long as similar fish bred and raised by long time breeding hobbyists or farms. It's all in the genetics of the fish. Good quality fish are not cheap, so you have to weigh what your pocketbook can handle.

Hope this helps.

 

[flitabout]

You are still overstocked. I agree that daily water changes of 50% are needed until your ammonia levels reach 0.