Don't know what this brown algae like is

[Kaykarr]

I'm getting this brown algae like substance spreading all over my tank walls and rocks, what is this and what can I do to reduce it? It's slimy and Ive tried to wipe it away just seems to spread more everytime I wipe it away!!

[mnemenoi]

Diatoms? Maybe using tap for water? RO will eliminate nuisance silicates and excessive minerals.

[Austy16414]

Agreed with Roy. RODI should fix it, but also look in to your lighting and your water parameters. Nitrates, phosphates, and silicates can all feed it, and your photoperiod could be too high

[Kaykarr]

I did use tap water, could be the reason why... I'll look Into the lights, nitrates and all the others! But what's the quickest way to eliminate it or reduce it from spreading?

[Austy16414]

Assuming it is diatoms, they make silicate removing compounds that will remove the silicates and essentially starve the algae, just make sure you follow all the instructions on the bottle. I think Seachem's Phosguard might work, but I'm not positive on that. Make sure not to wipe the algae around, as you'll just spread the diatoms through your water column. If you decide to clean it by hand, just move straight to the top of the tank and out of the water. Give your tank a good vacuuming. Is this a newly setup tank? Could it still be cycling?

[Kaykarr]

Yes it's a new tank, still could be going thru the cycling process!

[Austy16414]

That could also be factoring in. Find a way to remove your silicates, and then stick to RODI for your WCs