Single Betta, New (presumed Cycled) Tank, But Not Happy / Eating....

Hello all,

I have been doing a fish-in cycle of a single betta in a 25 litre, heavily planted tank. Which i felt (perhaps now incorrectly) would not be an issue for "Cousteau" the fish. Having thought I was over any stress causing problems and the tank was cycled, my Betta hasnt really been eating. Anything.

It had bacteria and plants added for seven days before the little Betta arrived and since then the test levels have been good.
- Very low to no ammonia / nitrates
- Constant 7.2 ph
- 80 degrees...
- Baffled filter.

My nitirites are way up. Im still doing daily 6 or sometimes 9 litres water changes, being very careful to match tempertaure, decholrinate and add API quick start to the right proportions.

Chomped down on his Atisons pellets on days 1-2-3 but now, over a week on, he's less flarey, much more reserved and whilst im removing most of the few pellets I have been adding, and trying twice a day to feed, he's not happy, or hungry.

Am i missing something, should i try some treaty-bloodworms?, almond leaf? and most importantly am I hurting our new addition?

Is he just settling in?
Am I stressing hime with over thinking the chemistry and water-changes?

Seems to love lounging foliage at the top of the tank, also quite happy to take a dive and explore so not like he's gasping by any means. Gills are not i overdrive.
But is defo becoming less active.

Any advice readily accepted, thanks in advance...

I know you said you added bacteria before getting the betta but most brands contain the wrong species of nitrite eaters so that might be the cause of your nitrite readings, depending on which one you used.
Just how high are your nitrites getting? If they are reading 5 that's as high as most testers go so they could be anything higher than 5.
What is the nitrite level 30 mins after a water change (the 30 mins is to allow the new water to mix in thoroughly)? If it isn't down to zero after a water change you need to do another, and possibly another to get it to zero. Enough water changes should be done to get nitrite down to zero and keep it below 0.25.
What are your tap water readings for ammonia, nitrite and nitrate?

I must admit that with a heavily planted tank you shouldn't really have nitrite as the plants should take up all the ammonia made by a single betta leaving none for the bacteria to turn into nitrite.

I would not worry about the betta not eating until after the nitrite issue is sorted out.

If ammonia is staying low, that shouldn't become a problem. 1 ppm ammonia is turned into 2.7 ppm nitrite so nitrite shoots up higher than ammonia.

Keep up with the water changes, and aim to get nitrite down to zero when you do them. The levels will stay at zero eventually