Another cause of nuisance algae(hair, cyano, etc.) is too much nutrients in the water. One of the ways to fix that is with water changes. You need to do water changes once a week. Taking out 40-50% of the water and replacing it with clean premixed salt water. This will help lower your nutrient level and also help lower the bad stuff in your water. You will need to do consistent water changes with a SW tank. It will keep your tank healthy. With your fish you can feed them once per day. I would keep going with the krill but also you may try some other foods like silversides, mysis shrimp. Your fish like variety in their diets too. You need to make sure the clown is getting his share of food instead of just getting what the puffer doesn't get to. Also, if any krill drops to the bottom and doesn't get eaten within a few minutes then it needs to be removed. Don't let it sit there to rot. Not good for your water parameters. Your tank doesn't need to be lit more than 10 hours a day. Now your substrate is crushed coral. How fine is the coral crushed? Does it still have large pieces of shell in it. If it does you may want to investigate a different substrate. Crushed Coral are notorious for trapping uneaten food and deitrius and causing high nitrates in your tank. You need to read the sticky at the top of this forum entitled Crushed Coral is a Problem waiting to Happen.
