ok you said you checked your "levels, they are normal, Ive got water lettuces in there that's evened out my nitrate level I was for a while having issues with that"
what were your exact readings - - nitrate is not the level you have to worry about. Nitrate is actually safe in certain quantities. You want to be concerned with ammonia and nitrIte. Any readings over 0.00 ppm is harmful
When you say you clean the filter- how do you clean it exactly? You should not be cleaning it every week and it should never come in contact with tap water.
And you are not going to be building an Ecosystem. Even a fully planted tank would need water changes - - you do not have a fully planted tank and should still be doing 25% weekly.
Water changes should never be skipped - they are simple to do and are for the frogs benefit.