Darn Diatoms!

[Riptide]

I have my lights (110W PC) on 8 hours per day. The aquarium is cycling right now. I am getting a real nasty growth of brown cyanoalgae that is covering my substrate and also my live rock. With the exception of one piece, most of my live rock is still curing (and cycling the tank). Tank is a 55.

I understand this problem is normal with a new tank. I used tap water to start off with and I am assuming there were lots of silicates in the tap water.

Should I keep my lights off for the next two weeks while the tank settles? Will this help kill it off? Will it kill the good algae that is still growing on my live rock (the pink and green stuff) if I turn the lights off?

[mogurnda]

The coralline algae on the rocks will do fine with the lights off. It's usually best to cycle in the dark to avoid the bloom you're experiencing. You may want to try to siphon off some of the scum in the meantime.

[Riptide]

Thanks. I'll keep the lights off as of tomorrow. It's good to hear that the nicer shades of life on the rock (pink & green) will probably make it.

I'm going to do my first partial water change this weekend and put fresh carbon in there. If after christmas the water tests out good then I will put the lights back into the picture and put my clown back in the tank.

There isn't much to siphon off yet - it's brown all over the bottom but it's more of a thin sheen rather than tuffy growths. So siphoning probably wouldn't pull much of it out of there. I'll try anyway though this weekend when I do the water change.

[llebcire]

As you might remember, I had the same problem as you about week 5. As of now, I am just entering week 8, and the diatoms are receding.

They seem to have gotten worse the first few water changes, but now are going away on their own, and life is coming back to some live rock that I thought was wasted (combination of diatoms and fallout from cc/dsb conversion) when it was completely covered with diatoms.

Just wait it out!

BTW-I too initially filled with tap, but have used RO ever since. I've had fish in the tank the entire time and have been using 220w pc on a 75 for 12+ hours a day since the beginning.

[Riptide]

Thanks for the suggestion and I also am resigning myself to be patient here.

To be honest, I don't mind if the entire back wall of my tank gets covered in green algae. It gives the fish a snack and doesn't look all that bad IMO. This brown stuff though... yuck.

The big thing to me is that eventually it goes away on my rocks and gravel. I'll be replacing at least 25% of the water w/RO this evening. By the time the tank is done cycling and my new rock is done curing (after christmas) hopefully the brown stuff will be on the way out. The only fish I'm going to add back in will be my maroon clown assuming he survives and gets better (has ich right now and is in QT).

I have plans to add a wrasse but that will wait until after new years.