View Full Version : DIY Live Rock - PH problem

09/30/2017, 11:12 AM
Can anyone who has made their own live rock from oyster shells and portland cement give me any tips/feedback? I made my own rock about 6 weeks ago and I still have a ph of 11.00. I have a pump circulating the water and a heater to keep the temp around 80, but it's still ridiculously high. I knew it was going to take some time, but i thought I would have had a much lower ph by now. I still get daily material accumulating on the water surface.


09/30/2017, 11:45 AM


I have not attempted this myself, but here's a thread that you may find useful.


Is your container well ventilated? The curing process requires lots of CO2 from the atmosphere.

Good luck!

09/30/2017, 12:48 PM
Well...lots of water movement, but maybe not enough gas exchange. Ill try adding a power head.

09/30/2017, 01:23 PM
I used my monster DIY skimmer


09/30/2017, 02:16 PM
Thanks Karim...read everything...wish I had before...picked up numerous tips. One the best diy tanks I have seen and well explained. I wish I had used type II portland cement n hindsight. I had seen too many videos saying it had to be the perfect white. In hindsight -- and with a little experience - it seems irrelevant once the Coraline algae takes over. Ill try to get more CO2 in there with an old HOB skimmer.

09/30/2017, 02:24 PM
I think is good to cure a DIY rocks soaking them in water with added some amount of acid like a vinegar.

09/30/2017, 04:12 PM
Acid can weaken the concrete unless very well controlled. Injecting fresh air is the equivalent of constantly dripping just the right amount of acid to maintain a pH of 8.

09/30/2017, 04:51 PM
Karim, if you don't mind. The rock that I made is a ratio of 3:2:1 (Cleaned oyster shell, Portland Type I cement (Leigh) and large rock salt). I just switched the bin that I am soaking the rocks in as I know the residue was affecting the readings. I have been soaking the rocks for about 5 hours now with a pump, 2 air stones and a heater. The initial water reading was a 8.0 It has now risen to to 9.4. Since I have been soaking them for 6 weeks now, I am wondering if taking them out and exposing them to sun to fully stop the curing process would help?

09/30/2017, 05:38 PM
Why would you want to do that?

Just aerate more until the pH stabilizes around 8

09/30/2017, 08:35 PM
Well...I did two small pieces that I let dry about two weeks ago and I had read on another forum where that was recommended. Like the acid bath, which I think just exposes the top layer of cement, I am a bit skeptical. The two pieces that I dried are currently lower in PH, but that may just be due to the fact that they have been soaking/curing longer. I don't really know whether drying stops/seals in the PH leaching out. Ill see what results in a week or so with better aeration.

09/30/2017, 09:12 PM
Drying concrete prematurely weakens it. It develops to full strength when wet.

6 weeks should be enough time, but I never air dried mine. I just allowed it to continue to cure in water.

10/01/2017, 06:56 PM
You need water in order for concrete to cure. If you try to dry it out, it won't cure. The molecules in the portland cement are undergoing hydration, calcium hydroxide is a byproduct and is what raises the pH. If you do something to slow down or halt the hydration process, you're either ending up with really weak concrete, or partially cured concrete that will just resume curing the next time it gets wet (ie when it goes in your tank).

Really, there are no shortcuts. Aerate the water if you're in a rush. I've also put the rock in large mesh bags and left it in the creek behind my house. I've heard of people putting small pieces in their toilet tanks. Really, anywhere that has water - and if the water is constantly refreshed or aerated, that's better.