My guppy was previously in another tank (100 l)
how long: 2 years or more.
water temp: 25 C
tank mates: guppies (10), neons (12), 2 gouramis, one bottom feeder.
food: vitakraft premium flakes, once a day.
every weekend: bottom gets cleaned, 30% of water and 1/3 of the filter.
last time: this sunday. but the guppy was already sick. 30% cleaned.
water conditioner and other products: JBL Biotopol, waterconditioner, JBL Denitrol aquarium starter
added anything: yes: after some test the nitrate en nitrite levels are too high so now I have to give them this (Dennerle aquarico BiActive) everyday (2x/day) (in the filter system)
water test: ammonia: I don't know, its not shown I use Tetra teststrips 6in1, the ph levels were good. like I said, nitrates and nitrites aren't good.
treatment: Well the onliest thing I could do was take the sick guppy out of the big tank and put him (slowly) in my other tank (water conditions are better, no nitrates or nitrites).
the behavior: he stays on the bottom, doesn't swim straight, heavy breathing, very hungry (although I gave him everyday enough flakes for one guppy- finished within the 5 min).
I guess the nitrates and nitrite level were just wayyy too high for him, but I don't understand, he's the onliest one that has this problem, all the fish don't seem to show any symptoms..