What is this brown coating in my tank?

[Heathers.why]

In the last week I have been getting this brown coating in my tank. My water quality is good per the fish store. My lights are on 10 hours a day. I have a clean up crew consisting of 2 claims, a serpent star fish, a sand sifting star fish, 5 turbo snails, 20 smaller snails, 5 emerald crabs, 20 red and blue legged hermit crabs. 5 blennies, and a peppermint shrimp, and a sea urchin. I feed once a day... Tank has been up for 10 weeks now.

 

[Heathers.why]

In the last week I have been getting this brown coating in my tank. My water quality is good per the fish store. My lights are on 10 hours a day. I have a clean up crew consisting of 2 claims, a serpent star fish, a sand sifting star fish, 5 turbo snails, 20 smaller snails, 5 emerald crabs, 20 red and blue legged hermit crabs. 5 blennies, and a peppermint shrimp, and a sea urchin. I feed once a day... Tank has been up for 10 weeks now.

The picture

 

[Squidly]

Whats the tanks flow like? If your sure parameters look good then it may be a result of a dead spot in the tank if theres low flow.

 

[Heathers.why]

I have two filters and a power head. When I feed the food pushes rapidly around the entire tank including the sand level. Should I add another power head?

 

[Massimo]

Is the tank fairly new?

 

[Heathers.why]

10 weeks

 

[Massimo]

It's diatoms, it's completely normal for a tank that's been set up for 10 weeks. It'll go away eventually. Pain in the butt but we all go through it!

 

[Heathers.why]

Thanks everyone... It sure helps to have people to ask as reading doesn't always help. Just wanted to be sure I hadn't done something wrong

 

[Massimo]

If anything, you can cut down on the amount you are feeding to your fish, my pleasure to help ?

 

[Heathers.why]

I am sooooo confused on how much to feed. Everywhere I have been has given me a different set of instructions :-/ I do have variety for them so I alternate mices shrimp and brine shrimp. The first store said feed them one cube twice a day but when I did it was wayyyy to much and they weren't eating it after five minutes. The next store said 1/2. Cube twice a day but they ate at night but not in the morning. So now I am doing 1/2 cube at night and they seem to eat it all in about 1 minute. Should I cut it again?

 

[Massimo]

Holy crap!!! 2 cubes a day?!?!!?!!??? Jesus, that's a lot of food! I feed my fish once every 2 days. Half a cube every 2 days is fine. Is your tank a reef or fowlr? What size, how many fish and what kind of fish?

 

[Heathers.why]

It is a reef tank. 90 gallons. It has a peppermint shrimp, a serpent star fish 20 red and blue legged hermit crabs, 2 claims, 20 Nass snails, 5 turbo snails, 1 lawnmower belenny, 2 scooter blennies, 2 red blennies, 1 sea urchin black, 2 OC clown fish, 1 blue hippo tang, 1 yellow tang, 1 foxface, 1 purple oro, 1 banner fish, 1 sand sifting star fish, and a beautiful pink sponge of some sort that hitchhiked in on the live rock that someone here said may not survive,

 

[Massimo]

Ah okay I see why they would say feed 2 cubes. However, 2 cubes is still to much in my opinion. 1 cube is enough for your fish. Do you let the food thaw out before putting it in the tank? Or do you just throw the chunk of food inside the tank and let then pick at it?

 

[Heathers.why]

I thaw it out and spread it into the current so everyone gets some

 

[Massimo]

When you thaw it out, you use the water from your aquarium correct? I figured out that the when you thaw out the cube, the juices that thaw out are filled with stuff that algae loves. What I do is I drain out that juice, and I just feed my fish the mysis/brine. Anyways, you're probably not doing anything wrong, diatoms are very common in new setups.

 

[MINItron]

Diatoms consume silicates that are common in new tanks. They can even be eating free silicate from the surface of the glass when it is new. There is also a certain amount of silicate in the rock and substrate.

 

[Bectan01]

I would also suggest a slightly shorter photo period, perhaps 7-8 hours a day?

 

[Heathers.why]

Including blue lights? I have one hour blue lights then 8 white then 1 hour blue light

 

[Bectan01]

Oh that's not too bad. I run slightly less but just see how you go, I agree that new tank/diatoms is what you have

 

[MINItron]

There's really no reason to have the actinic lights on longer than the white lights. If the diatoms don't subside on their on soon then it is likely that your water source is contaminated with silicates, you are feeding with something with silicates (not likely) or some rock in you tank has a higher than normal amount. This is not something that most aquarium test kits test for. It is separate test. Most phosphate removing media will also help remove silicate if there is a significant amount.