Soaked rock

[steveoutlaw]

I built a nice arch out of some dried rock and portland cement. It's been soaking for 3 weeks in a tub of fresh water outside and I've been changing the water about twice a week. Is it safe to put it in a tank to cure now? The only inhabitants of the tank are live rock and some xenia. Tank has a refugium and skimmer on it.

[zygote2k]

test the ph of the water and see what it is- it might be fine or you might have to wait for a spell.

[Chris-]

Depends how big the arch is and how big your tank is. I threw mine in after a week of toilet flush changes. I had about 1/3 rock in a 90. Everything was just fine and dandy. Just toss it in and check the PH every hour. Throw it in tomorrow morning and watch it with the PH meter. If the waters PH has not gone up in 12 hours or so, i would say your safe, however....... While water is fine, any shrimp that hide on/under may not be okay. I did not think about this when I threw my shrimp in. Quite a few died and I chalked it up to when I saw one sticking out of of bluespots mouth ( I always got the small shrimp), so, not sure if it was him or the PH that did them in. Seems all my shrimp lived after he was gone, but that was a year after the rock went in. I never thought about doing a test or to check them for shrimp safe-ness. Just a thought, though, everything else was fine.

 

FYI - Made a sealed concrete (eccept for the entrance/exit) goby sleeping cave and threw that right in the next day. Goby was used to sleeping in it and faired just fine.

 

I have no theoretical proof, but, I think saltwater binds, seals, locks up the PH to a degree. You figure, I put 1/3 of pure concrete rock in my 90, which according to my bucket stated that in 24 hours the PH would go up to 10/10.5 . I decided to play devils advocate since I have a lot of flowing water and figured the PH would bleed off, and, sure enough, not a .1 change in PH . Your mileage may vary, but, those were my results. I tossed the other 1/3 of rock in the next week, same cure time and same results.

Edited June 4, 2010 by Chris-

[Origami]

What you're looking to avoid, Steve, is a big upward shift in pH due to the cement curing. You're probably going to be fine, but try putting the rock in a bucket of fresh (dechlorinated tap but not RO/DI) water and see if it shifts the pH sky high. If it does, you'll need to cure (soak) it longer. If not, you should be safe to put it in your tank. You can use regular tap water for the test, but if you do, be sure to give the rock a good rinse before moving it to a tank with a well-developed biological filter just so you remove any residual chlorine or chloramines from it.

[flowerseller]

I'd be more concerned with rising ALK at this point.

[steveoutlaw]

It's a large arch that will just fit diagonally in a 20g tank and will be about 1" under the water so it will take up about 1/2 of the tank. Again, looking to cure it properly before putting it in my display tank.

 

Mods - please move to General Discussion forum.

[Origami]

I'd be more concerned with rising ALK at this point.

That'll show up as a pH shift.

[flowerseller]

That'll show up as a pH shift.

 

True, but the ALK can raise substantially higher than the pH will indicate.

[Origami]

True, but the ALK can raise substantially higher than the pH will indicate.

It does seem that way sometimes. For example, an alk shift of 1 meq/l or 2.8 dkH equates to a pH shift of around 0.1 units in salt water. In fresh water, though, the pH shift is more dramatic because there's far less buffering capacity available.

[Mountaineer]

I agree with checking the ph for a change. It is probably fine, but I would check it to be safe. If you don't see a change you know your OK.

[Chris-]

Whats the PH showing in the holding tank after a 12 hour refresh?

[flowerseller]

It does seem that way sometimes. For example, an alk shift of 1 meq/l or 2.8 dkH equates to a pH shift of around 0.1 units in salt water. In fresh water, though, the pH shift is more dramatic because there's far less buffering capacity available.

 

good thing it's not a Ca reactor with a pH of 6.5 and an ALK of 19-40

[steveoutlaw]

It's still testing at 8.6 which is the high end of the scale. I think I'm going to leave it in for another week and then move it to the curing tank.

 

Thanks for all the advice.

[Chris-]

8.6? Thats sweet! I dumped mine in at 10.6 and all was fine (remember, it was an experiment), lol.

[Origami]

It's still testing at 8.6 which is the high end of the scale. I think I'm going to leave it in for another week and then move it to the curing tank.

 

Thanks for all the advice.

 

Leaving it for another week's a safe bet. However, with the buffering capacity of saltwater, you'll probably be fine. I doubt that you'd see much of an alk boost or a pH shift at this point.

[steveoutlaw]

8.6? Thats sweet! I dumped mine in at 10.6 and all was fine (remember, it was an experiment), lol.

 

 

I don't know if it's any higher than 8.6......that's as high as the scale on my test kit goes. I'll put the rock into the curing tank next weekend.