Diatom crazy

So my tank has been set up for a while now and I just recently noticed that I have a diatom bloom. I do weekly water changes so I don't think that's the problem but I don't have a phosphate test kit I ordered a test kit online because nowhere around me sells them do you have any suggestions on what I can do to get rid of it I haven't added any new equipment recently everything's been constant since it has been set up.

What are starfish or something that stirs the sand bed help at all

 

Serpent starfish and nassarius snails will do the sand stirring. As for the rocks and such, get a few chitons depending on the size of your tank.

 

Diatoms feed on silicates. Once they have consumed them they will disappear. If you want to help clean them up a little try some blue leg hermits. Serpent stars can get over a foot in diameter. I would not reccomend a sand sifting star. Nassarius snails or a fighting conch are best for stirring/cleaning the SB.

 

How many for a 55 gallon?

 

Actually one fighting Conch should be enough or about 4 nassarius snails.