Bleaching rocks right in the tank?


New member
I've been battling with hair algae for more than a year. There was so much hair algae that my tank looked like moss planted tank. *I've tried many things including raising magnesium and turning my lights off for many many months, but as soon as I turn the light back up, the tank is covered with hair algae all over again. So finally I gave up and took the whole tank down and starting everything over from scratch.*

I've let the rock dry out of the water for over a week in hope that it would dry and kill everything. But now I'm not so sure. *The problem is, the hopefully dead dried rocks are now stacked up beautifully in the empty tank. So, I continue to bake them under 400w metal halide bulb.

Here are the questions:
1. Are the hair algae and other bad stuff really dead?
2. Should I still bleach them just to be sure no nasty stuff is coming back?
3. If so, can I just add water and bleach to the tank? The rocks are already beautifully stacked up, and more importantly, I've already paid the guy for setting them up. >..<


In Memoriam
Drying will not kill the algae nor the potential phosphate in the rock. It will likely resume upon hydration. Need to take out a large rock and put it in clean water that's proven to test free of phosphates

In 4 days test the water for po4, if it registers then a clear direction can be taken


New member
Thank you for the advice. The tank is now empty except the rock formation, no sand, so water. Can I just leave the rocks in there, add RO water and test the PO4 after 4 days?


Premium Member
You could try soaking the rock in RO/DI for a while. I would add a powerhead to prevent anaerobic microbial growth, which can have a strong odor. In addition, lanthanum chloride solutions like Sea-Klear will precipitate the phosphate in the water, if there is any. After the phosphate was gone for a while, I might treat the rock with bleach to kill any remnants, but I'm not sure that it's worth the effort.


Staff member
RC Mod
You didn't say you'd tried gfo (Phosban). If you are sure about the TDS of your ro/di (s/b 0 ) and use a gfo reactor, you should see the end of the algae in a few months. What's going on is that your rock and sand (and possibly some water) came in with a load of phosphate, and hair algae loves it. The sand and rock can only leach out a measured dose into the water at any one time, and when it's gone, it leaches more out...until it runs out of phosphate. Your best bet is to run it out of phosphate entirely, by running the reactor until you notice the green is going---or by Bertoni's good advice, above. A tank needs a little phosphate, but your tank seems to have cornered the market.


New member
I've also tried phosphate reactor (but I think it was different brand) for many many months, but it also didn't work. I now believe that the rocks came in full of phosphate. They came from unknown source and the first water was real ocean water also from unknown source. I've tested the phosphate level, can't remember how much exactly, but I remember it was just slightly high. But one thing for sure, the magnesium level was outrageously low.