Coral slowing getting smaller

[Jackg962]

Several of my corals appear to slowly be shrinking, I beleive one is a zoanthid and the other a toadstool. The first picture was around March 10 and the latest is todays picture. It is a 65 gallon 9 month old tank with a protein skimmer. I have run the t5 lights from day 1 for 6 hours and acninitics an hour before and after. h20 parameters appear normal, CA 480, Alkalinity 6.7 KH, MG 1320, PO4 is now .5. Around middle of April i found out about phosphares an they were at 2 then. I would have thought the coral would have started looking better. I change about 10 gallons every 3 weeks. Any tips for me folks?

[flametailblenny]

I didnt see any pictures, maybe im missing something

[thegrun]

How many T-5 bulbs do you have on the tank? You might want to increase the photo-period to 8 hours on your daylight bulbs and see if that helps. The alkalinity is low, I would try to get it up to about 8-9 DKH. I'm an advocate of smaller more frequent water changes, 5 gallons weekly would be good for your tank. The 10 gallon changes could shock the corals with a sudden change in parameters.