Sand Bed - Too leave alone or not to

[Dwb859]

I have 2 inch sand bed in my aquarium and have been experiencing a diatom bloom on my sand for a few weeks. My tank has been set up for a year and a half. I've been vacuuming the sand and it seems clean but then the diatoms come back, even with about 50 hermit crabs. Do you think I'm causing this problem by messing with the sand? What would the sand be releasing to cause the bloom? I have plenty of live rock in the tank and very low nitrate and phosphate levels. I have no algae anywhere in the tank except for the sand. I even change my ro/di cartridges every couple of months to be on the safe side, my product water contains 0 TDS. The tank (150 gallon) has two tuzne 6105's, which seems to be more than enough flow. I have to angle them up to prevent the sand from moving. I'm doing a 10% water change every two weeks. Change out carbon and GFO monthly. Feeding small amount of frozen every other day and nori daily (2 tangs, majestic angel, two clowns.)

Does stirring up the sand remove the bacteria from the surface of the sand causing a bloom? Similar to the glass getting algae because there is no bacteria on the glass vs. live rock? The reason I ask is there is a 4 inch sand bed in my refugium that i've never touched and it stays spotless with 24 hour light and macro algae. I hear some people say they never touch their sand bed and others maintain it by siphoning/stirring.

[Dwb859]

Can a mod please fix the title to read - To leave alone or not to

[billwill]

I never siphon, but I stir it up a bit when I start to get some cyano or whatever else growing on it. It's happening because you're not getting enough actual flow across the surface of it. I've got a couple sand sifting stars too, and those seem to do a pretty good job. Your powerheads turned up slightly are not getting enough flow to the bottom. You'll have to live with blowing sand for a little bit until it clears out and moves what it's going to move and enough bacteria colonize on it to keep it in place.

[Dwb859]

Originally Posted by billwill

I never siphon, but I stir it up a bit when I start to get some cyano or whatever else growing on it. It's happening because you're not getting enough actual flow across the surface of it. I've got a couple sand sifting stars too, and those seem to do a pretty good job. Your powerheads turned up slightly are not getting enough flow to the bottom. You'll have to live with blowing sand for a little bit until it clears out and moves what it's going to move and enough bacteria colonize on it to keep it in place.

The reason I angle the powerheads up slighty is because I have that much flow across the sand bed. These powerheads give a wide flow and any particle near the sand bed is moving quickly in the water. They aren't aimed at the surface of the water or anything like that.

[Dwb859]

I do notice bubbles under the sand along the glass. Is this the gas that anaerobic bacteria converted? I only have a 2 inch bed and wasn't sure if they could live in those conditions.

[JohnniG]

Have the same problem. I stir it up though.