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Lonnie
06/09/2008, 09:43 PM
I am beginning to get a caramel colored substance on my rock. It looks like diatom algae, but there is none on the sand. Is this possible, or is it something else?

I recently had a bad carpet algae problem & could not get it to die off after numerous water changes. Imade the mistake of letting it "burn itself out"... only got worse & made me waste tons of salt/additives. Of couse the water parameters were perfect when I had algae.

After slowly scrubbing, cleaning & bleaching all my rock (& leaving the tank covered in total darkness for 2 months), the nasty green algae is gone & the coraline algae is finally coming back. Everything was going very well for a few months.

Now the still white part of the rock is getting a slight tan color. Parameters are: Nitrate 5, Phosphate .01 or lower.... the test kit barely changes color. Everything is remaining stable.

Lights on for 3hrs a day & near darkness the rest of the time.
Actinic 3hrs, 20K 1.5hrs.

220g tank
55g refugium
30g sump
Skimmer, UV, & filter sock changed daily
Using RO/DI water for changes.

Any suggestions or ideas? I can leave it dark again if necessary. The fish are fine.

Thanks in advance.

rivoth
06/10/2008, 12:00 PM
When my new tank went through its diatom bloom it was mostly on the rocks and hardly any on the sandbed. My Trochus snails kept it cleaned up pretty well and after a couple of weeks it was almost completely gone. Turning out your lights will certainly slow down the diatom growth, but until the disolved silicates are used up you are just postponing the growth.

Generally Diatoms outcompete other algae until they use up all of the disolved silicates in the water. Your bloom however seems to be happening after your tank has been running well for a while. This begs the question of what is the new source of disolved silicates.

If you've added any new live rock that would be one explanation. If the resin on your DI is wearing out then you might be introducing disolved silicates through your water changes. Some people have reported diatom blooms after dosing their tank with iron.

Some Cyano can look like diatoms but that usually grows at the points of lowest circulation. I would not expect your rock to have worse circulation than your sandbed.

Hope you can figure out what is going on.

Lonnie
06/10/2008, 07:29 PM
The tank has been in use for approx 8yrs, but I recently (over 1 month ago) cleaned all the rock.

The algae that originally consumed my tank was similar to a green brillo pad that would not die from darkness & was impossible to completely remove. This is why I started bleaching the rocks.

I did 1 rock every day (by bleaching for 1 day, rinsing, then bleaching again, then rinsing & soaking in clean water for 1 day, rinsing again, soaking for 1 more day & finally letting them dry for a week before returning it to a totally dark tank (wrapped with blankets in a dark room). This took the better part of a month to accomplish this, but did not crash the tank or disturb anyone inside.

I recently added some new aragonite to the bottom, but this change was almost 3 weeks ago.

My RO w/ 2 stage DI is working very well, with a reading of 1 on the meter.

I've been adding 2qts of kalkwasser mix per day.

As for the diatom algae, or whatever it is, it comes off with a soft paint brush. It seems to only grow where the light hits it (top & front), there is nothing on the side of the rocks against the back wall or those shaded from above.

I'll try to leave the room lights on for a few hours per day, with the tank lights out & see what happens.

The bad part is the coraline algae is starting to grow nicely & I do not want to stop it.

Any suggestions?

rivoth
06/13/2008, 08:49 AM
I can tell you that my Trochus snails did an excellent job of keeping the rocks clean during my diatom bloom. I'd imagine that many other rock based herbivore snails would do as well. During the later stages of the growth I was seeing a lot of initial coraline growth on my rock. That was with 7 Trochus snails taking care of 50 pounds of live rock.

So with the right snail crew you should be able to keep your lights on for the coraline algae, while still keeping the diatoms from getting out of control.