At the time I posted my numbers were .50 ppm for ammonia and .25 ppm for nitrite and 20ppm for Nitrate. And yes live plants are present although they tend to constantly die (and then I replace) How does this make a difference if I may ask? Just curious.
Live plants need nitrogen, and most aquatic species prefer it in the form ammonia/ammonium (not nitrate as one still reads). Plants will take up ammonia/ammonium faster than the nitrifying bacteria, which is why a good supply of fast-growing plants can "silent cycle" new tanks. So in a case where you might somehow remove most of the nitrifying bacteria [not saying you did, just if you did] the plants would still remove the ammonia/ammonium. Now, here this wasn't adequate if the ammonia reads above zero. But then I do not know what plants, or how many, or how thriving they are. Plants like slow-growing Java Fern or Java Moss for example willobviosly not be removing that much ammonia, bjut thriving stem plants and especially floating plants do.
Now that we have numbers, it would seem to me that your over-cleaning may have contributed. Adding new frogs would likely impact the existing fish and frogs, adding stress from them, as well as the new frogs changing environments. The food block may have contributed another factor. When all factors are added, the system shows weaknesses.
As for the frogs that died (well disappeared since I found next to nothing of them) Is it possible that since the tank had been going for so long 5 years with the same occupants. That they just weren't accepted by the tiger barbs, are tiger barbs even smart like that? I don't have a ton of snails in the tank I find it hard to believe they ate up every bit of the perished frogs in the time my parents came and started checking up on the tank. Both of the frogs were chunky healthy frogs.
I am only suggesting possible causes, things that occur to me from your information. I don't know much about aquatic frogs, but they can carry disease and may have. I recall reading years ago that when an amphibian tank is established, new amphibians should never be added as there is a serious risk of disease. I tend to think this is significant, considering the nature of amphibians. They may have rapidly died, and the other frogs and fish and snails would not hesitate to eat them.
I have read that frogs and fish should not be combined. Again, I know little about these aquatic frogs, or which you may have. There is some truth in fish being kept together in a less than preferred environment (tank size, species, etc) sort of growing up together and things working out better than one might expect. But down the road, add anything and it is throwing a wrench into the works.
Byron.
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