PH of water, Agrocrete

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Aquarium Advice Addict
Sep 8, 2003
Indiana USA
Hello all,

I am currently using tap water for my tanks. I have used tap water for my FO tank for the previous 9+ years and saw no ill effects except algae growth. My reason for the question is due to a batch of Agrocrete rocks we made about 1.5 month ago. We made the rock and it has been sitting in water and getting fresh water every day. From what I have read, you had to wait until the PH of the water came down since the portland cement will leach PH a bit.

I use a Aquarium Ph. test kit and my tap water tests between 8.2 and 8.6, usually on the high end - color is more blue than green. The water in the agrocrete container always tests between 8.6 and 9.0 - color is aways blue. Anyone have any experience with this? Also we want to try corals and such, will higher PH pose problems with this? We have snails,hermits and a CBS that as molted once in the tank right now and they are doing fine.
About the DIY rock, some say you gotta wait around 6 weeks, others say you gotta wait at least 12-15 weeks for the pH to settle. All I can say is, as you might already know, pH grows exponentially and not linear... If an 8.1 has 100 parts of acidity, and 8.2 will have a 1,000, and 8.3 will have 1,000,000. I really don't think you fish and specially the corals you're planning to add will survive a 9.0 pH. Just give a few more weeks for it to settle. You know what they say... in an aquarium, only bad things happen fast.

My tap water tests at 8.6 and the reading I just got from my tank was that or higher. Could be wrong time of day but not sure.

I think you shoudl try another PH test kit... Aquarium Pharmaceuticals is not a very accurate test system IME.. in some cases mine were a full point off...JME

Might want to try SeaChem or Salifert...
Thanks, I will do that. The tests seem to be ok but I can never get my Ph to come out right.

Aquarium Pharmaceuticals is not that great? Great, I just purchased their kit.

I am not saying it is terrible, I bought 1 of their kits for PH a while back and it was off by a point to Salifert... I contacted AP and they sent me a new kit and it also tested off by a point.. Always showed the PH being higher than it really was.. when you test your water at 9.4 or so, it tends to freak you out... So from now on, no more AP for me.... This was just my experience....
I like the pH test kit from Seachem. It is quick accurate and also comes with a good alkalinity test. I think you find it for around 9 or 10 bucks. I would shoot for a pH of 8.4 at the highest. At higher pH any ammonia present will be more toxic. For FO tanks the pH is not nearly as crucial as for a reef tank. High and low pH values affect calcium and carbonate solubility as well as coral growth rates. One question to be asking is what in your tap water is causing the pH to be high? It could be caused by excess chemicals that you don't want in a reef tank. Invertebrates are much more sensitive to chemical contaminants than fish. You may want to look into a RO unit or look around for a store that sells RO water from one of those machines.
I revived this thread just to state that the agrocrete I mabe in Oct. is still leaching. If I let the water sit for 2 days, it reads PH 8.8 - 9.0.

Thinking about just throwing the stuff out. My wife hates having the stuff sitting around. I have about 40 lbs of portland cement to dispose of too :(

Anyone made this rock with good results?
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