I have had my 29 gallon all live plant aquarium running since March 2010. I've had guppies and endlers since May 2010. They have been thriving for all of this time. I have amazon swords (reproduced to make 3 bunches), java fern, banana plant, dwarf lilly bulb (that has shot off tons of lilly pads all over the surface), some other leafy plant, and a HUGE mass of java moss that had taken over nearly half of the tank. I have a bubble wand across the bottom and a submergable heater that keeps the temp at a constant 78-80 degrees. I never have any algae problems. I have a good number of small snails that take care of that problem and I have 2 good sized green corys. I started out with about 5 males 8 female guppies and 1 male endler, 2 female endlers which became about 50 or so total over the span of 8-9 months. I do 25% water changes every 1-2 weeks. The weeks that I didn't do a water change, I would add water plus some stress zyme and stress coat to eliminate chloramine. The chlorine evaporates out of the tap water as it sits for a week's time.
Here is where the problem starts: Last week, I noticed quite a few fish were dying. No dropsy, no ich, nothing visual on the fish. Just dead fish. The fins weren't even torn or anything. I figured it was just old fish. Then, the numbers of deaths started increasing. I did a 25% water change last wednesday. Added some Nitraban, but not a full dose. I don't really like using a lot of chemicals. I tested the water and it indicated very high nitrates, zero nitrites, zero ammonia, ph about 6.2 and alkalinity low, water very hard. My water has always been hard for years and that has never seemed to be a problem for guppies. But the nitrates scared me! This morning nearly all of my fish are dead except for about 6 fry, 2 females, and 1 young male. One of the fry is a male endler (thankfully!). So thats about a total of 45 or so fish that have died since last week. I figured that the java moss is so big it has been holding a lot of fish waste and food and was keeping me from reaching some of the dead fish because theyd get tangled in it. So this morning, as I have the siphon tube in there, I pulled out ALL of the java moss and siphoned out some of the mess that made with food and debris floating all over the place. I changed 25% of the water (6 days after the last one). I threw the java moss in the trash and it had about 5 dead fish in it that I wouldn't have seen unless I pulled it all out. Now I can see whats going on in the tank! weew! I put the normal dosage of stress zyme and stress coat. After a couple hours I tested the water again, and nitrates have lowered to either safe or unsafe (on the border). The pink was so close to either, but its significantly dropped. ph is still 6, nitrites and ammonia still 0. The remaining fish look happier. The adult maile was acting limp before the water change this morning and now he is acting a lot happier!
Can anyone give me any advice as to what the heck happened? I'm assuming its the nitrates from dead fish that were hidden by the java moss. BUt my husband who majored in marine biology said the plant cycle should be taking care of the nitrate problem. Any suggestions about the ph? I've tried ph adjusting tablets in the past but gave absolutely no change to the ph.
Thank you in advance!