I made a batch of diy rock out of concrete/crushed oyster shells, it worked perfect but I had to spend about 3 months doing water changes in a container to get the pH down. I live by the water in Nova Scotia, I was wondering if I could put the rock there to cure? I know the water temp is WAY colder so there would be some die-off, but lots of rocks are filled with coraline algae here too, dunno if it would survive though??

i think i would be more worried about pollution and other "stuff" in the ocean

Yard boy did his "jetties" nano where he put his rock into the jetties near his city. that was tropical water though.

Just put the rock in the basin part of your toilet. The water changes every time you flush.

actually, if you're only tried cure the concrete and not bacteria, that's not a bad idea.

That's a great idea, assuming that you don't need much rock.


To answer your original question, The PH of sea water is about 8.3, while the ph of tap water is around 7 (6.5 to 7.5 depending). Uncured aragocrete will raise the ph in your tank. Since fresh water has a lower ph than ocean water, I would guess that it would speed up the cure as compared to ocean water. My knowledge of chemistry is spotty at best, but my partially educated guess is that your rock will cure faster in fresh water. You should ask a real chemist, because I might be proving the adage that a little knowledge is a dangerous thing.

You could try it both ways (some cured in fresh water (toilet tank?) and some cured in the ocean), and then after two weeks put the rocks in separate buckets of fresh water and see which one raises the ph more in 48 hrs, to see which one has cured more (the less the ph raise, the more curing has taken place). Your done curing when the rock doesn't raise the ph of fresh water at all. I'd love to know how such an experiment turns out.

Thanks for all the input. I want to set up a 90+ gallon so it's gonna take a bit of rock. I was thinking about the ocean because there is lots of coraline algae (not sure if it would survive at 78 degrees though), and im not going to need it until the spring so I do have lots of time. But if any of the bacteria/coraline won't survive the big temp. change then I guess freshwater might be a lot easier.

I'm unsure if the coldwater bacteria and coralline will survive in tropical waters. I'm sure someone more knowledgeable about this subject will chime in. As for the toilet basin I know a lot of people who use it to cure concrete frag plugs with no problem. Although 90lbs of DIY rock will be a tight fit.

I made a couple hundred pounds of white cement rocks this summer and the best way I found to cure them was to pile a bin full (I used a big cooler due to the spout), insert an airstone attached to a two liter bottle 2/3 full of water, sugar and yeast and to alternate between letting them have a couple days just moist with the CO2 all around them, followed by a couple days submerged with the CO2 bubbling into the water and a pump to circulate. As long as you are careful the water will never get below 6.5-7 pH and will never need changing this way.

I did testing with a TDS meter of the water I used and this actually leached very little/none out of the rocks (I kept reusing the same 5g of water for the wet part of the cycle too), whereas leaching in tap water or RODI waste sucks a ton of calcium out of the rocks.

All of my rocks were steamed at 160F for 24 hours a couple days after casting though, not sure if this makes a difference in the leaching process or just the initial cure.

~20 lbs of the rocks went in to my Sister's 50br roughly 3 weeks after casting and all the parameters have been spot on. The DIY rocks are already getting covered in coralline and the tank is ~2 months old now.