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From: R

I have done everything I know to eliminate the brown algae on my Live Rock and the tank. I've added the Phosguard to my canister mechanical filter. I have no phosphates, no nitrates and cleaned out the canisters. I scrub down my live rock (Is this bad? - I do it in a separate tank in water I will replace from my show tank) so my purple algae will show. All my other parameters are excellent. Ph-8.2 Calcium 475 Alk =5 Oxygen - 7.0 I am very happy with my Aqua C Remora-pro skimmer- I'm amazed at the crud it removes! Daily a cup full. Is my lighting not on enough? My 30W actinic blue comes on at 6.00am, my daylight and another actinic blue lamp come on at 10.00am and my 175W MH 10000 K comes on at 12:30 all go off between 10:00 to 10:45pm. I also am adding some "Reef Vital DNA" and "Spectral Vital" daily along with "Immuno-Vital Marine". I also add trace elements. I shortened my light on time and now have ugly brown algae and can't think of any other changes I've made to merit this horrid occurrence.

From: HL

Well, I'm no "Boffin" on algae, and can only speak from (limited) personal observation, but you could consider the following:

Stop adding all those supplements. If you do regular water changes (say about 10%-20% every 2-3 weeks), you should have enough minor & trace elements without having to add anything. Of course, you must still continue to add buffer and calcium, when necessary.

Confirm the accuracy of your test kits - maybe have the water analysed professionally by a laboratory and test the same water yourself for comparison. I've had a few problems with kits, where one brand new kit would show phosphates as 0, and another would show it as 0.5 ppm. I've also had the same discrepancy with nitrite, nitrate and calcium tests.

Brown "slime algae" (Cyano-bacteria) must have silica in order to grow. Use RO or DI water if possible, or at least filter the water through a household "purifier" such as "Brita" or "Nitragon".

Increase your photo period, and time of intense lighting. Using a hand-held photographic light meter, I've noticed that the intensity of natural sunlight at 7.00 AM is already much brighter than all my lights combined! An even simpler test - just shine some sunlight onto your tank with a mirror, and compare intensities. So, increase the lighting gradually over about 1-2 hours in the morning, and then give them everything you've got. Decrease again, as you do, over a period before "lights out". If nothing else, you will end up with GREEN algae, which IMO looks a lot better than Cyano!

Lastly, stop scrubbing the rocks. You are just killing off the small animals that could help by eating the algae. The algae spores are in the water, and they just settles back on the fresh, clean rock, and flourish with no natural enemies to keep them in check.

And, most importantly, BE PATIENT. You've only recently started with the new skimmer - give your tank a month or two to stabilise before adding / trying anything new.

From: SV

Brown Algae = diatoms, which are a silica based algae (they take silicon out of the water and use it in their cell walls). Depending on where you live, you may have lots of silicon in the water. Or you put sand (beach type) in your tank, which is a really fine source of silicon. (Mild sarcasm there…)

You can sample your tap water to see what you are putting in the tank (maybe your LFS will do it for you). You may want to consider getting a RO filter, or simply buying RO water from your LFS. Mine sells it for about 35 cents a gallon, which is pretty reasonable.

You can get rid of the brown stuff by cleaning the walls of the tank, and rinsing off the decorations in your tank. I don't think it is dangerous or bad, just ugly.