Fully cycled setup. Hello I've been having some issues in my tank where every time I do a 50% water change there seems to be diatoms throughout on the ornaments and glass after a few days. Tank ammonia levels are 0 nitrites 0 and nitrates around 20. I usually vacuum the tank every time I do a 50% water change which is done once a week on 120 gallon. It's easy enough to clean off but a pain to take ornaments out every week. I use regular tap water and only have a fluval 306 and 2 sponge filters. Any other information I can add to help lmk.