<a href=showthread.php?s=&postid=6747228#post6747228 target=_blank>Originally posted</a> by Infern0
diatom algae in my opinion.
That seems reasonable like a reasonable guess, but it's very definitely grey, not brown.
Carefull attention to water levels.
The tank has been rock solid for a long time, in terms of nitrite, nitrate, ammonia, and pH. The salinity changes, but is generally between 1.022 - 1.024. I've been trying to keep it closer to 1.024 since I began reading RC, but a water change can lower the salinity by .002 if I misjudge the volume I am replacing and am trying to make a correction of any sort.
Large water changes with RO water.
Given my budget, I have not been able to afford RO or RO/DI. However, I've begun purchasing RO/DI water for water changes weekly, though I only do 10% weekly on average.
Definitely watch water sources when doing changes and follow proper changing techniques.
I don't know what proper changing techniques mean. I've begun mixing water 24 hours in advance and aerating it, but if there's more to it than that, I'm probably not doing it.
This with vigorous skimming should take care of it.
A skimmer is in my future, but at least a couple of months away. I took a part time job just so I could make improvements to my tank.
I do change 2 of my 4 filters in my, don't laugh, TetraTec PF300 every 2 weeks or so.
You can GENTLY brush the affected area of the rock if you ensure to remove algae debris. By gently I mean, you can't get it all off, just raised portions.
Is a toothbrush okay? I hope to reaqauscape all of the LR this weekend because I've picked up a mini-jet 1200 and built shelves out of egg crate and PVC pipe. I also intend to do a 25% or greater water change with RO/DI water while doing a thorough cleaning of the substrate. Would you recommend more than 25%?
Here's another picture:
It looks very much, to me at least, that the rock itself is colored grey. The white streak on the very right is not sand or substrate, it's another color the rock has turned. The white strip is thin and runs from top to bottom on one side. The natural color of the rock before it entered the tank was a very even beige color. I remain puzzled, but will try your advice.
As you can see in the picture, other algae is on the rock, including what I hope is the beginnings of coralline algae. Slowly but surely the rock has been getting purple flecks.
Here's another picture that more clearly shows the original color of the rock.
