algae out break??

Hey guys, I have a problem with brown algae in my new marine aquarium.

I have tested all levels and they are very good, just a little phosphate, less than 8 similar levels with nitrate.
The tank cycled 6 weeks ago and has not looked back.

I have tried three additives including phos guard, none worked that I can see.

I run a skimmer not while phos guard or the others were in there, canister filter, a refuge,a third of tank in live rock and the few fish and all corals are doing great!

Any ideas.

I would say you have the standard new tank syndrome tod.
Most new tanks that have a lot of clacium based product either as substrate or live rock will get a diatom out break because of the slilca that will be part of your problem.
The next will be the unstable PH as your system becomes mature,the co2 from this action will fuel the brown algae.
The water changse at this stage and your skimmer need to be done well until stability is acheived.

If you are realying on live rock for most of the biological work in your tank than that will be part of it as well because live rock will give you a far more unstable start to the system when not using external filtration properly.

Hope it goes well for you!

Agreed with above. All new tanks go through a brown and red algae stage.

What are your tank specs (Volume, Tank size, pH, Amm, Nitrite, Nitrate, Calcium ect)?