Ok, I've got a 75 gallon community tank that i established in June. As of a month ago, the stocking was as follows....

10 Zebra Danios
10 cardinal tetras
10 rummy nosed tetras
4 panda corys
6 peppered corys
2 german blue rams
red tail black shark
4 clown loaches

I started going with some low light plants, and everything was going fine. Then, one day, i came home to a tank full of dead hornwort. A bunch of it got caught in the crevices around my tank and starting rotting, causing an ammonia spike that started killing fish. I quickly lost my shark, 2 panda corys and 2 peppers. I tried daily water changes for a week, but kept losing fish, so eventually, i stripped the tank down, took out every speck of rotting plant life and ripped out most of my other plants just to be sure (all thats left now is 2 crypts that are about 5 inches tall) I changed out roughly 75% of the water vacuuming all the debris.

So for a few weeks, everything looks ok. I lose 1 more panda cory, but i figure the worst is over. Everyone has perked up and color has returned.

Then, this week rolls around. I come home on tuesday to find one of rams has pop-eye. The next day, it was worse and eventually i euthanized it (it was floating on the bottom and had badly labored breathing.) It was very hard to do. Now, this morning, i find another dead cory. I check the water, and its saying i have like 2 ppm of ammonia. I don't understand how this can be possible. I think that maybe my test kit is bad. I go and get another one, and it says that i have over FOUR PPM of ammonia!!!

I have done weekly water changes of 25% since i started the tank. I use water conditioner every time. I have enough filtration for 150 gallons(added a 2nd filter to increase water flow on the left side of the tank) I only feed 5 days a week and i do not overfeed. (all food is gone withing 5 minutes) The tank has almost no algae and the water is crystal clear. It has been almost a month since i rid the tank of plant matter, yet the deaths are still trickling in. What the heck should i do? There are currently no signs of disease (unless you count 1 cardinal tetra who doesn't have very good color)

Here are some current tank pics (i just threw all the fake plants back in there after the major cleaning, so it doesn't look very good.) I just ordered a new T5 lighting system for a real shot at raising plants, so it will look very different in a few weeks. I want to start re-stocking, but I can't justify it with fish still dying.

Tank pic(although i just changed to a black background)

another

one more

Any help would really be appreciated. I'm assuming i should really ratchet up the water changes, but it doesn't seem like it would do any good without knowing the cause of the ammonia in the first place.

This post has been edited by tlef316: Jan 28 2008, 03:38 AM

Have you replaced the filter media lately?
Uhm... washed the filter out in tap water? Or maybe washed it out too much in old tank water?
Have you tested your tap water for ammonia?
I don't think that would really cause anything though unless there was alot in it though. We have a .25 ammonia reading in our tap but it's never caused a problem.

Uhm.. I dunno.. just throwing ideas out there.

Have not replaced the filter media.
Have never rinsed it in tap
I squeezed it out in tank water when i did the big cleaning, but that was 3 weeks ago now, and all i did was dunk the media in the bucket and squeeze out the sponges real quick
tap water has a negligible amount of ammonia (less than .25)

Appreciate the input. For what its worth, tank temp is like 74 degrees and Ph usually hovers between 6.8 and 7.2

I wish I could be help to ya.. I just hope everything works out and your remaining fish survive!

Could a chemical or something of gotten into the tank(kill bacteria)?

Do you have another tank or anyway to get mature media, it would help a lot to get rid of the ammonia.

i don't see how any chemicals could have gotten into the tank. nobody besides me goes in there. We had our carpet shampooed like 2 months ago, but the problems didnt crop up until like 5 weeks later when the hornwort exploded.

No other tanks that i could get media from. Even if i did kill ALL the bacteria (that seems like a pretty big If) I find it hard to believe that it would take this long to grow back. I find it even harder to believe that rummy nosed tetras, cardinal tetras and clown loaches wouldn't have been affected. It just baffles me. Everything I've read said that the rummy nosed would have been next to go after the pandas (if there was indeed a problem) but they haven't skipped a beat. Its like I've got 10 Rudolph's in there. They are as brightly colored and as happy as can be (see the pic above)

This post has been edited by tlef316: Jan 28 2008, 04:56 AM

What water conditioner/ dechlorinator and testkit are you using?

API master test kit. API Tap water conditioner.

i have no idea but i have heard that using air freshners or the plug in types can kill fish????

sounds very odd though, hope you find out what it is soon, you have a lovely tank .

Sharon

is the pump/filter working ok, no blockages or hugely reduced flow caused from plants blocking the pipes or something?

what are the ammonia, nitrite & nitrate reading from the test kit at present ?

both filters working fine. Nothing obstructing water flow.

I'm just about to run out to work, but I'll take some readings this afternoon and post them. (need to stop and pick up more water conditioner as well)

that rules out lack of flow and oxygen killing of the bacteria in the filter then, it does sound like something has killed off the good bacteria though and started the cycle again ?

you could have been unlucky with your local water source. while some contains no ammonia most of it will fluctuate depending on the seasons and things like equipment at the water conditioning plant wearing or being replaced. As such there are occasions where one of the levels in your local water will spike drastically and may be at a high level for a day or so then return to normal. So it's possible something liek this happened the day you did your water change there was uber high ammonia in it for some reason and that's got into your tank. If the ammonia is above 8ppm then bacteria growth will be inhibited by it which could then account for it taking a week or so to clear up.

really there are any number of reasons why this could have happened, but the solution is pretty simple, lots of big water changes (test the water before you put it in) until the ammonia is back to 0.

test your water daily for now, and after it's calmed test it weekly for a good couple of months, see if you see any more fluctuations.

Hmm, i suppose this is possible. I'll start doing daily water changes of 25-30% Hopefully everyone else survives until the levels return to normal. thanks

25% water changes are useless when dealing with ammonia. What you want to do is 75-80% water changes daily and cut the feeding right back. Make sure the new water is free of chlorine and has the same temperature as the tank. Check the PH as well because ammonia is toxic in alkaline water (PH above 7.0) and is harmless in acid water (PH below 7.0). If your PH is very alkaline (above 7.5) then add some sodium biphosphate (PH Down) to the new water and bring the PH down towards 7. If the PH is around 7.0 then don't worry about changing it.
Cut the feeding back to once every few days and only a tiny amount. The fish will be fine without food for a while and the less food the lower the ammonia levels will be. Also don't feed any frozen food until the problem is solved as meat foods produce more ammonia than flake foods.
If all goes well the ammonia should go down in a week or two and then the nitrite will go up and down. Keep the feeding down until there is no ammonia or nitrite readings.

This post has been edited by Colin_T: Jan 28 2008, 01:57 PM