Thanks again, NancyD, plaalye, Farid.
afroturf wrote:wow, that last piece of wood is the nicest I've seen fake or not. I'm going to be making a fake rock structure, background and some large boulders for the bottom.
What would be the best way to waterproof and to make the polystyrene look like rock? I'm torn between cement, epoxy resin and sand....
Thanks.
Now if you use polystyrene, I don't think you need to waterproof it
an sich. Or any of the other materials you mention. They are all waterproof in the meaning of not dissolving in water.
Judging by your questions on your thread, you seem to have reservations for usage of cement in aquarium. That's ok, cement does affect aquarium water by raising alkalinity.
Or even worse, if you put uncured cement into aquarium, ph may rocket to even 10 or higher. Depending on amounts of cement added.
But. Cement-based decor has been used in aquariums since way before any of the nice epoxy resins and other materials we have today, with no ill affects. Fish have been raised in pure concrete (cement-based) tanks and pools. Well, I don't get any royalty for cement sales, so I'll leave it at that.
What I have done in the over 25 years I have used cement in aquariums is I have made sure it has been cured thoroughly before adding it into the tank. Curing depends on the thickness of the layer and only happens with water. If cement dries, curing halts. Wet it again, and it goes on from where it was left.
Even after curing, cement raises alkalinity (and hardness) slightly, but with normal water changes I have never had any problems with it.
Some people seem to treat cement with vinegar to neutralise it quicker. I have never tried it, but I'm sure it does the trick. Acid does neutralise alkalinity.
That being said, any of the materials you mention are worth trying. Or combining. I used to put a layer of (clear) epoxy resin on top of my cement scapings, but don't any more. I get a nicer look without it. But I have seen other people getting very natural looks with epoxy, too.
I also sometimes mix coarse sand in cement that I use, to get a nice uneven texture... And Farid mentioned he puts sand on top of uncured (I think?) epoxy resin to lose the gloss.
What I do use often these days with cement is acrylic polymere. They are airdrying plastics (usually 1-comp) that are used in all kinds of modified cement materials and also sold separately. They make cement-based products stronger and seal it to an extent.
Here's a brackish tank I have, with what I think is a very nice ambiance.
Background is leca-cement covered with grout and the roots are pvc pipe with grout. Except the few live mangroves...
