Mysterious Fish Deaths

The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.

cloudgazer

Aquarium Advice Apprentice
Joined
May 3, 2009
Messages
12
Location
Canada
Hey there,

So, say you've got a 36 gallon fresh water community tank. It's over-filtered, has excellent lighting, and is well planted with live plants. We supplement the plants with C02 only (1 bubble per second, on a timer with the lights so CO2 doesn't run at night) and the temperature is kept at a consistent 78 degrees.

Weekly water changes of 30-40%, and water quality is stable. Ammonia, nitrates, nitrites are all zero, and the ph is stable at 8. Though this is high for the majority of the fish in the tank, it's consistent so that shouldn't be a problem.

Say that this tank has had fish dying, with few if any symptoms, pre-maturely and without any apparent cause.

So, this is basically what's going on in our community tank. It has a few dwarf gouramis, a few cory's, neon tetras and a few guppies. It previously had a betta, but it was one of the recent fatalities.

The tank has had a fish die every day or so. I briefly thought it may be due to aggression from the betta, though he's never displayed any towards the fish that I have seen, I thought it may be possible in the night when we don't see the tank he might be bullying the fish.

Now that he's dead, that definitely rules out him as the cause. We also had a dwarf gourami (the variety referred to commonly as "honey") die this weekend, and another neon.

Our guppies just dropped too, and a couple babies survived.

I'm really grasping at straws now. We're going to try and have the water tested for contamination (my girlfriend's sister tests water quality) but I'm pretty sure that's going to turn up nothing of interest.

I've done a biopsy one the gourami to see if I could spot anything abnormal or unhealthy looking. Everything looked healthy, no swim bladder problems or any odd colouring. (I've done dozens and dozens)

Well, I know it seems like the only answer is some kind of mysterious fish assassin is sneaking into my tank at night, but, barring that, does anyone have any idea what could be the problem?

Our local water in my city contains chlorine and chloramine, and we of course condition the water for changes.

I follow all the proper protocols, so this mysterious problem is very frusterating for me.

Any help is greatly appreciated!!!!!!
 
You might try an oxygen flush.... seems like there may be a lot of Co2 in the water.... do you see any of the fish gasping or breathing heavily?
 
No gasping at all. We have two HOB filters running, but I suppose I could get some extra oxygen in there with a bubbler or something.

The tank has been running for about a year and a bit.
 
Well too many bubbles will release your Co2 faster... you might just check your Co2 levels and see if they are allright. I was thinking about it at work and had read another thread similar and the person had found their heater was shorting in the water. ...... just a couple thoughts.
 
Very unusual to have zero nitrates if the tank has been running that long, even with plants.

If your plants are healthy and growing, they are producing far more oxygen than the waterfall type filters will provide by agitating the water's surface. Do any plants 'pearl' during the time your lights are on?

I'd get a new test kit (if you use your own) as it might be giving you incorrect readings. Or get the water tested at an aquarium store, most will do testing for free.
 
Have you run carbon to remove any possible contaminants?
 
Hmmm... Heater shorting... That might be a possibility.

Well, the nitrates aren't zero, but they are very very low. The test kit shows minimal.

The plants do indeed photosynthesize, I've got them on a good light cycle.

I just returned from vacation, and we lost another guppy, but she had just given birth, so I am not sure if I can consider it a mysterious death.

I'll inspect the heaters and consider replacing them/testing to see which is faulty.

Thanks for all the replies thus far!
 
Back
Top Bottom