Help: SPS bleaching and STN

[Myka]

I would suggest you go to a water store and buy 40 gallons of RO water and do a couple 20-gallon water changes in the next week. Also, with STN I find a lower alkalinity level is often better. Your calcium and alkalinity aren't balanced btw either.

If you have too rigorous algae growth in your tank it will starve your corals of nutrients causing bleaching. Algae also release toxins of sorts that inhibit coral growth and can really harm corals if it is out of control. I've experienced this myself.

Another thought is that I don't think those MP10s are really strong enough on that size tank for SPS. I think it would have been better to buy two MP40s. If you have any more powerheads on hand you could try adding more flow.

For feeding, feed the corals in the evening jut before lights out and turn the pumps off for an hour so they can feed. Then by morning the food will be filtered out by your skimmer and filter sock. Filter socks tend to really help with cyano if you change them out every 2 days.