# Concrete and PH?



## Cappy (Feb 27, 2010)

So I saw this really nice concrete structure thing at the local nursery and thought to myself that would be a really nice cave for my fish to hide in.

Does concrete mess with the PH balance of the water? I recently had to add a few pieces of driftwood to the tank to lower the PH to a comfortable 7-7.5 for my Severums, so I'd hate to mess that up by adding something to raise the PH level back up.

Has anyone had any experience with this?

What other types of materials are aquarium safe and won't adjust my PH?


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## pistolpete (Dec 28, 2009)

concrete will raise the PH and hardness of tank water quite a bit. This effect can be reduced by letting the concrete cure under water for a couple of months. bubbling co2 during this process helps. another alternative is a muriatic acid bath.

I would only recommend cured concrete with african cichlids unless you want to coat the whole thing with epoxy.


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## iceblue (Apr 27, 2004)

Algae and bacterial growth will reduce the amount of hardness released by the concrete. As was recommended, allow as long a curing process as you can stand. Once it's in the tank keep track of your Ph and do large water changes as often as needed. Most Africans, especially Tanganyicans prefer a high PH and shouldn't present much of a problem as long as you keep the Ph stable.


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## PfunMo (Jul 30, 2009)

This is a frequent question that often gets conflicting answers. For me, I have never found too many things That I throw in the tank that change my PH. Perhaps the answer is that I have really hard water. The answer from others with less hardness might logically be different. I have found a site which gives me a totally different thought on how I would answer your question. Check this site and see if it may make sense of this question and then you can decide for yourself based on your local water qualities. Scroll way down to get the relavent parts even though the rest is also important to understand. Some things take five readings for me to get the story. 

http://www.freshwater-aquarium-fish.com ... mistry.htm


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## Cappy (Feb 27, 2010)

It's quite a large piece so I think coating the whole thing with epoxy is going to be quite an undertaking. I guess I'll just have to find some slate and silicon it together to get the cave formations I want.

Thanks for the feed back.


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## Shayne00 (Nov 17, 2014)

Made a corner cave piece out of 4" and 2" PVC elbows, spray foam, and weighed it down with concrete.
Made a much smaller version with the same materials without concrete, and it did not effect anything.
Currently leeching the item for the second day. Used tank water from my 55.
Tested tank water. Tested leeching water after 4 hours, then at 6 hours...
So, concrete took the ph from 6.6 to 8.2 in 4 hours. It's now at 8.4 after 6 hours.
Will test again tomorrow morning, change water, and test again. 
After about a week, and if ph is dropped, I'll be placing it in a 46 gallon with two bettas and a goldfish to use as canaries before it goes permanently in my 55 with convicts.


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## BillD (May 17, 2005)

For what it's worth, when i poured the concrete deck for my swimming pool years ago, some concrete got into the pool. the pH was radically increased to above the top of the test kit. It took a couple of quarts of muriatic acid to lower it to mid 7s. It was a very small amount of concrete, perhaps a shovel or two total. That was all it took for 23,000 gallons. Cured concrete will of course have less of an effect, but it is worth being cautious.


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## Mcdaphnia (Dec 16, 2003)

I put concrete items in a vat outside that was part hose water and part rain water. I added oak leaves, and passively, any tree leaves that volunteered. Some Gambusia added the food for nitrifying bacteria which colonized the concrete, sealing off the interior. After about a month, the concrete could be added to most tanks without affecting the pH. If you make your own concrete items you can use low alkalinity white Portland cement (used in stucco) and substitute long strand pet moss for about half of the sand or gravel. Called hypertufa, this material will become pH neutral quickly.


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## malawi.dave (Feb 5, 2015)

you could coat it with2 coats of pond sealer that worked for me when I made stuff for the marine fish I had 
also you can get different colours


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## Mcdaphnia (Dec 16, 2003)

Since this was already made, how long it has been out in the weather at the nursery affects the alkalinity of the concrete piece. Clear epoxy will have little effect on the appearance of the concrete. Pond sealers may be blue, black, or some other color.


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## malawi.dave (Feb 5, 2015)

Pond sealer also come in clear beside other colours


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## Mcdaphnia (Dec 16, 2003)

malawi.dave said:


> Pond sealer also come in clear beside other colours


Absolutely. Although clear pond sealer in my area is something new. There are also spray cans of clear sealant for leaky gutters that a person who loves to experiment could test out.

I have a mermaid figure which I am having coated with clear glaze and it will then be fired in a kiln. If it doesn't blow up, I'll let you know how that works out.


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