So... I'm having an issue I'm sure many people have had before and I just can't find a way to get it to go away.
My 120 litre tropical tank has had an ammonia spike and it refuses to go lower than 0.50ppm; granted, it's better than it was and it was actually off the charts and killed five of my fish, but... I'm still not comfortable. Any ammonia is bad, after all.
I don't have the other readings right now as it's quite late and I might wake people up if I start fussing around, but last time I checked, my PH, nitrates and nitrites were all within safe levels. The only problem is the ammonia.
The temperature of my tank is 76-78°F. I use a Fluval U3 internal filter with high oxygenation, along with two amazon broad leaf plants. My substrate of choice is a smooth pebble-like gravel.
The fish I have left aaaare;
Two very young Kissing Gouramis
One Red Honey Gourami
Three veeery large Zebra Danios
One Weather Loach
The fish that died from the ammonia spike were;
Two Panda Garras
Two Red Shiners
One Chinese Algae Eater
I feed them a mixture of Tetra Pro Energy and Tetra Pro Algae in small bursts; most likely two to three crisps (which are pretty tiny) which I then crumble to allow the smaller fish to eat it; they always finish within a minute and I make sure there's no waste. I used to also feed them with frozen bloodworm and algae wafers, but since my bottom feeders have died, the wafers don't get completely eaten and I don't want it to add to the problem.
The tank has been running for a couple of months now, as I upgraded from a smaller 64 litre one.
I've tested my tap water and there is absolutely no ammonia, so that's not the problem.
I use API StressCoat to get rid of chlorine and chloramines, and I add API StessZyme once a week. I also add Evolution Aqua Pure Balls but not as often or as much as it says on the packet as I've noticed they leave little husks and it's quite messy.
I've done several water changes every few days; mostly 25% and a few 50% ones. I also cleaned the filter using tank water but only once as I don't want to overdo it. I vacuumed the gravel every time, too.
I tried using Interpet Ammonia Remover, and while it got rid of the huge spike I had that caused the fish deaths, it hasn't done anything to help my problem now. I just can't seem to figure out the problem and it's driving me nuts!
Any tips would be appreciated; I'm very worried that my other fish will die and I'm very attached to them. Especially my little honey gourami, Tiki. He's such a friendly lil' guy. :c
Please and thank you! ;A;
Bonus Photo; one of my Kissing Gouramis!