The ammonia wasn't bad but the nitrites were at the highest end of the scale 3 weeks ago. Worked really hard at getting them down and were finally normal when we got them tested beginning and midweek. Don't have a test kit as normally get the water tested at our local shop, the man there is really helpful and has been doing it 27 years now si I trust him lol.
We bought the tank second hand with a couple of fish already in it (2 kuahli oaches, plec, 3 golden barbs, 2 bloodfin tetra, a red fin shark that we gave away, a sailfin molly also given away after wrong advice and an Apple snail).
We transported it with 1 third of 'mature' water in and trusted when she told us she had just cleaned filter. I filled with conditioned water. My husband against my advice added a further 3 mollies and some guppies.
They really weren't looking good after a few days and developed fin rot after being nipped by shark.
I had the water tested and everything was high except ph. Turns out there was hardly any filter media in and what was in there was so old it was brown. It was all coarse with no bio media, nitrate sponge and carbon, they were all completely missing.
Bought all new, left 2 sponges in with the new ones and had water checked twice a week since with water changes.
Sorry for long post!