How long should MH be on for????

I have 2x250 watt metal halides on my 70 gallon and i have had algae issues. I have to scrape it off everyday with my magnet and where i cant reach its like plaster. I have it on for 8hr 30 min a day on a timer. Whats the problem??? Its a reef tank too with tonz of coral!

 

You have too many nutrients. Maybe you feed too much. The light cycle is already short, so I doubt that would be a cause. I leave my lights on for about 12 hours a day.

 

i feed 2 times per day only seaweed algae for my tangs.......grrrr i even have bio balls so it can't be too much nutrients!

 

Have you cleaned off your bioballs recently?

 

nope... never have.

 

Then your problem is excess nutrients caused by detritus accumulation on your bioballs.

 

That'll do it.

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A couple tangs fed a couple times a day could poop up a 70 in a hurry.

 

Do you only have halides on for 8.5hrs? I have a 12hrs cycle that starts with actinics for the entire 12 but MH's are only on for 10. Also you could be over stocked, try stepping up the water changes. Plus I only feed once a week on my 75g...

 

I have had a horrible week. Toadstool, bubble(slowly coming back), and now clam are dead. Just checked and my shrimp is having a feast on the clam. I have heard that pulsing xenias pulse when they have nutrients and just when all of this happened, they stopped pulsing. Is anything making sense here or do they have any sort of a connection???? Also just checked and my bio balls don't a single speck on them. Clean as can be and i got them months ago????? i am sooooo mad. What is happening to the tank??????