Dry rock causing GHA?

[bluey]

Hey guys just a quick question here. We bought some pretty cheap man made dry rock that basically was a large chunk of sandy concrete. We used it for about 6 months or so. Everything was going pretty good but we noticed the rock was actually disintegrating over time. By a significant amount. Corals would actually fall off of their spots they were glued etc. We also started having significant GHA growth even though I was running enough carbon and phosphate remover for a tank 4 times that size. Overfeeding was not the issue as I cut down and the GHA kept accelerating on growth. Reduced lighting and no effect. Massive water changes and sand sifting had no effect.

My question is this. I know concrete has silica in it and I'm wondering that by using that really cheap substitute, as the rock was eaten away more of this silicate and other materials was continuously being deposited in the water making the phosphates go nuts even with all that remover. We already bought new and good rock and just installed it today (carribsea life rock). I just want to know if anyone else has heard of this?

 

[Roosterjack]

Interested in this as well. I purchased a lot of used dry rock from someone who had been out of the hobby a few years. It was obviously once "live rock" at some point, but when I got it the rock was bleached white and dry. I read somewhere here in some thread that old rock can release things it absorbed when in a tank. Not directly comparable to your situation but close enough that it caught my eye.

As to silicate, I think that is more associated with diatoms than GHA.

 

[Duffer]

It’s not the rock per say but your phosphates and/or nitrates are too high, if they are testing low than that means your gha is consuming it

 

[attiland]

I doubt that rock can release significant amount of phosphate or nitrate. Silicates maybe if not the right kind of sand been used. Easy to test it though. Run the rock in a bucket for a few days and you can measure what comes out of it.

 

[mcbdz]

I say it can be the rock. We ordered the cheap man made rock online and added it to an established tank and over time evrything started doing bad. Took the rock out and decided to break it up and just add to sump. It was so thick we couldn't break more then little chunks off it and tried to drill it and it just made mud. Want get that ever again. Now dried old live rock I would use juse cycle it.

 

[bluey]

SO....just to follow up on this post...YES cheap butt rock CAN cause phosphate leeching....we replaced the rock and no longer have any GHA at all....SO you all know now