Hi! need help with high nitrate

[Darcytulullah]

Hi everyone, please ignore the title I realised this is not the thread for that question.

I’m new to this forum so I’m sorry if I make any mistakes. I’m relatively new to fish keeping (less than a year) and I’ve up until now been doing pretty well at maintaining my one 54L tank which is stocked with 9 guppies, 9 cardinal tetras and 5 false julii corys. This tank has been running since October 2019.
I have a 150L and 25L currently cycling also with hopes of having a single betta in the 25L and something fun in the 150L, open to suggestions for this. Both of these tanks are planted with live plants which I’ve always wanted to try.

[Autumnsky]

Hello and welcome!

Sounds like you are looking at getting decent sized tanks for the fish.

Are you familiar with the nitrification cycle? The link in my signature has an article helpful information.

You can try more frequent water changes for mitrates, vacuuming the substrate especially under where you feed the most, reducing feeding amounts permanently or temperarily, split the feedings in 2 or 3 servings so it doesn't hit the tank all at one like with one feeding, rinse filter media with treated /dechlorinated water or use chemical means which might be the last option if the others don't help enough.

Nitrosorb is one I have used.