In my filter I have four levels with a pre filter sponge. Bottom is bio sponge second level is ceramic media Third level is carbon pack and last level is filter floss. I will definitely be looking into a hang on back refugium or skimmer. I thought the phosphate wasn’t bad but I was wrong. It is 0.5 I think my lowest has ever been was 0.03 I wish I kept it there. I just added a lot of dry rock after I upgraded my tank. I kept the old rock I had though. Thank you for your very informative response as I needed to know this stuffFluval may not be keeping up with tank as it is a mechanical filter only which is why I asked specific questions. UV will penetrate shades and blinds and curtain- the power of UV will surprise you. Back to filter:
The issue with using canister filter is that it is your primary source of filtration which is mechanical and you want to have mechanical , biological and chemical to manage proper water quality. The power filter will polish water and trap particles via the cartridge. It also can promote nitrates and even phosphates.
Chemical is what traps and breaks down chemical compounds such as feces and uneaten food often accomplished carbon and GFO
Biological is what utilizes the natural process of biological filtration such as use of ceramic nuggets, bio blocks, and microscopic bacteria surfaces.
You are lacking some forms of necessary filtration. A hang on back refugium, even a hang on skimmer such as Ice cap K1or K2 series will work flawlessly and help with overall waste removal.
On your phos- Is it .5 or.05 ?
keep a pouch of ChemiPure Elite in your canister to help with Phos control.