- check PO4 level. If high add Phosphate remover.
- if its a newly setup tank, this is normal. They should go away after 2 months.
- add in sand dollars, they help to turn over the sand.
- get snails to control algae
- Do WC more often. Use DI water. If you are using NSW, check the PO4 level in NSW. Some are high.
- reduce lighting period to 6 hrs
- manually perform sand mowing periodically.
good luck bro!