Building materials

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Hi, I want to mold a special piece of scenery for my tank and I'm looking for a material I could mix that would not affect the water. Most recipes I found contain cement wich I know rises PH.
Has anyone built something for their tank with cement and seen how it affects PH?
Or has anyone a scret recipe I could use?
 
Marine epoxy is safe for coating sculptures and decor for fish and reptiles. I've even heard of people making tanks out of wood and waterproofing it with the marine epoxy. They've had fish in these tanks for over 20 years, with no problems. I'm sorry that I can't be more help and recommend certain brands, but this is a start.

~Aaron
 
What are you trying to make? If it can be somewhat flexible like semi-hard rubber then mixing sand or fine gravel with aquarium silicone and casting that can produce some interesting effects. Getting a mold that aquarium silicone doesn't stick to is a headache and a half. You can buy it in caulking tube sizes at some fish stores or have them order it for you. It can be gotten in black as well as clear. (Clear works a little better when adding sand and gravel, black is nicer for attaching rocks and plants together to make you scenery.) If you come up with a more rigid material to use I'd be very interested in hearing about your results. I can tell you from experience that you can seal cement, but you have to make a really good job of it on completely cured cement. It isn't as easy as it sounds.
 
I'm trying to build a fountain and aquaduct, it's a pretty big set-up. The silicone sounds like a good idea, although it might not be stiff enough to hold the weight on top of it. Have you ever tried it? If so what did you make the mold out of? I wonder if plaster would do it. I don't think rubber would stick to plaster.
And no I don't think I want to seal my cement, I don't trust that it would hold for a long time.

I'm planning on making tests with cement mixed with sand and gravel to see how much heightens PH. As water gets acidic over time, I'm hoping they will even themselves out, the again maybe I'm dreaming. I'm hoping someone from the forum has already done such testing, or found a dream material.
Silicones sounds good though, thanks!
 
I'm not sure silicone is stiff enough for what it sounds like you're building, it depends on how thick you make it. Plaster molds work but it releases better if you use a coat of nonstick cooking spray. Then of course you need to clean the finished piece. Remember that silicone needs to air dry so it doesn't work very well in a closed mold, and thicker pieces can take a long time to dry. Yes I have made a few pieces, I finally decided that they were more trouble than they were worth for what I was doing. Now I just glue rocks, gravel, plastic plants etc to frames made of pvc to build the shapes I want. Have you thought about using pvc as the base for the aquaduct? I'd be interested in any test results you got. I had really nasty water quality problems from very small pieces of cement which were unknowingly stuck to some slate tiles I used once. Good luck, I'd like to hear more about what you are putting together.
 
Thanx,
I can see how sticking pieces of rock together would work well for a natural set-up but I've been carving small animal faces as fountain heads so I really need to cast a mold, both positive and negative. I was thinking of adding gravel and colored sand in layers in the mixture to make it look like a real rockface that had been carved.
I suspect it will be a couple of months yet until I get the whole thing finished and find a proper material but if you've had problems with cement, then maybe looking into plastics is the solution. I'll do some reaserch.
Did your cement "melt" and stain the water or did it just affect PH?
 
I removed the cement before it had time to do anything but affect ph. There is a place in Portland Oregon called stevensons pattern supply which has an incredibly helpful lady who knows all about various resin and plastic materials for casting. If you can't find anyone local to help you, you might try them.
 
Wonderful!
I know a guy who works with resins too so between him and her and Internet, I should find something. Persistance is my moto ;)
thanx for the help. I'll make sure to post my results when I find something that's workable.
 
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