# Fiberglass for cave habitat tank?



## pupfish (Jul 25, 2006)

I have been discussing an idea for a tank with the kid at the aquarium store and he keeps insisting I can sculpt my own stalagmites for my blind cave fish tank myself out of standard fiberglass repair kit material (like Bondo for cars, I guess) he obviously hasn't tried it himself. I'd also like to make stalactites that are glued to the cover and hang down into the water, and possibly a thin submerged backdrop imitating a rock wall, although I may end up painting on the back of the glass to get an effect of depth into darkness. At least I won't have to worry about algae, since this will be kept in a room which is naturally very dark unless I'm in there using it. 
Now every time I go to the store he's all excited and has another angle to the idea, including covering the sides and top of the tank with a flintstone's type shell leaving just a window in the front, and putting led spotlights shining down like holes of sunlight. I admit I like some of the ideas quite a bit. Expense, expense...My other idea is to use conical glass bottles covered in silicone and rolled in sand for my rock formations? Any suggestions? I'm starting with an old 40 gal acrylic tank which is scratched up pretty well and needs a new cover built for it anyway.


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## YzMxer99 (Jul 17, 2006)

Ok, I do have some fairly good experience with fiberglassing random shapes being a certified prosthetist (artificial limbs) and I will tell you how I would go about doing it. It ain't going to be easy though. Keep in mind that I have never done a salagtite before, and I don't know how the resin will affect the fish.

1) Make a mold out of 20 min casting plater. Start by filling a paper towel tube with the 20 min casting plater. You mix it with water until it is a creamy consistancy.

2) Once hard, shape the stalagtite using a stanley sureform (half round). When you get the shape you like use some sand screen to sand it smooth. Use a wet rag to whipe off the residue.

3) Let it dry for a couple days

4) Now comes the tricky part, you have to seperate the plaster from the wet resin fiberglass layup. In prosthetics we use Poly-vinyl-acitate (PVA) to cover the mold. I would use PVA, but it will be hard for you to get. If not, you could try a plastic bag, or a really thick coating of mold release. The mold has to be really dry to attempt this. 

5) Use acrylic resin and paint it onto the fiberglass (this part is going to get really messy) You have to work real quick as the resin has a 5 min max work time. 

6) I would then place a bag over the stalagtite, seal it, and place a vacuum pump to the bag. Pulling about 20 mmHg vacuum.

7) 20 min later it should be hard, take out the stalagtite, now its time to cut off the "big" end and chisel out the plaster.

8) Now you have a light, hollow stalagtite. As for finishing, i.e. painting and texturizing I don't know. Just keep in mind that if you glass a tank, it will keep degassing for a week. Don't paint and texturize to soon, let the gasses escape

Good luck


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## kaj41354 (Jul 20, 2004)

This link http://www.max-discus-dream.de/mddnew/3D-back.htm may help you. It is about using fiberglass resin and styrofoam to make rocks and backround but the methods used may help


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## onemyndseye (May 12, 2006)

Yeah... The resin will be inert once it cures. Some people built plywood tanks this way (everything is plywood except the front)... built the "box" then waterproof it with epoxy or fiberglass resin..

Sounds like a interesting project  Good Luck! 

-Justin
One Mynds Eye


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## kitbasher (Aug 29, 2006)

I have not use fiberglass for aquariums, but I have made speaker surrounds with fiberglass resin. I made forms for the speaker pods out of extruded foam, and covered them with two layers of aluminum foil, for use in a tank I would use a differen mold release, maybe two layers of painter's plastic tarps. For the bulk of the material to support the resin I used scrap sweatshirt material. I bought it by the pound at a local sewing store. It lets you build up mass really fast. For strength I alternated the layers of sweatshirt material with layers of the glass fiber mat. Once the resin was set I cut it off of the mold with a saber saw and sanded the surface for painting. Good luck and remember to do this work outside the resins give off nasty fumes while they are setting up.


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## YzMxer99 (Jul 17, 2006)

kitbasher reminded me of something, if you are going to sand you are going to itch. Period, no way around it. Those little fiberglass splinters get into any exposed skin and sometimes even covered. Have a bucket of sand around and when your done, rub the sand on your arms, it will help with the itching. keep us updated


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## schaadrak (Aug 18, 2006)

Maybe try using a foam cone as the core, that way you don't need any cast releasers.

Is regular cement okay to use in FW tanks? If so you could use hypertufa instead of fiberglass. It would be more stone like.


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