Hi all I've got a vision 180 tank and no matter what i do my levels are never right. All my fish seem healthy, touch wood and so do my corals apart from sun coral which I believe is underfed. So feeding it up now. once a month I do a 54 litre water change. I've recently added seachem matrix to try and reduce nitrates. I regularly add phosphate remover. Ive removed internal filter and all the assembly housing. I have removed all the noodles week by week out of the canister filter, non left now. Ive cleaned the sponges in dirty water. Ive taken the sand bed down to 5mm - 10mm (dont want to take it down further because i have a chalk goby). Alk: 15.6 dkh ph:7.8-8.0 calcium:455ppm nitrate: 50 nitrite: 0 phosphate: 0.2-0.5 magnesium: 1260 please can someone give me advice to get my levels right.