View Full Version : Using Clay

05-01-2009, 5:50 AM
I know Terracotta pots have been a long time staple of fishkeeping and considered (usually to be safe).

What do you know about making your own clay caves/sculptures etc...?

They have oven-bake clay- where you can fire in your own oven at 350F for an hour to harden (not as durable as normal terracotta- but what wear and tear will it get inside an aquarium?)

Is that a safe clay to use?

There is also regular terracotta clay- we have an art store down the road that fires artwork by kids and whatnot in a kiln - I might be able to get them to let me use their kiln (I'm sure for a fee).

For wedding cakes- you can find at art stores moulds for pillars- can make some impressive "parthenonic" caves using them and some clay.

05-01-2009, 2:31 PM

The kind of clay you bake in your over is something called "Polymer Clay"- it's actually from a material standpoint closer to "PVC" as in PVC Pipes then it is Clay. Originally invented as an insulator and was discovered by accident to be able to be used as a modeling clay with a low- firing temperature.

They have different chemical properties based on who makes them. The chemicals of concern are "plastisizers"- which public opinion is mixed on whether these are bad or not.

I've e-mailed one company to ask about the toxicity of their product and whether they are suitible to use underwater/use in aquariums.

These products are frequently marketed towards kids for crafts- so you'd hope they non-toxic. If anyone is interested I'll let you know if I hear back. If these turn out to be safe could be a fascinating easy new tool to use for making caves and aquarium decorations.

05-01-2009, 2:34 PM
That would be pretty cool!

05-01-2009, 2:44 PM
Polymer clay is not fish safe from what I've read. I have heard that epoxy clay is ok, but you'll want to check up on that too.

05-01-2009, 2:52 PM
I've been doing some more research on this and found a lot of conflicting arguments.

Some people say it is not safe BECAUSE of the plasticisers- however sculpty (brand) claim the plasticisers are all removed during curing.

Most people who say it isn't safe say so because it is labeled as "not safe for food". However, the makers claim the reason it is not safe for food has nothing to do with it leaching chemicals but because it is porous and harbours bacteria. (like everything does in the aquarium).

I've read numerous accounts of people who have used this in aquariums and measured the water chemistry day by day with no problems- and kept fish with no harmfull effect.

It sounds like it is safe- and basically just turns into PVC when fired as long as you cure it properly- don't fire it at too high a temperature... and most of all... make sure it is properly cured.

I will be doing more research though before using... it sounds viable.

05-01-2009, 3:14 PM
this would definitely be cool to know! man I can think of such neat caves and hides I can make for my fish just on my own! and can you imagine how cheap it would be!?

05-01-2009, 4:41 PM
this would definitely be cool to know! man I can think of such neat caves and hides I can make for my fish just on my own! and can you imagine how cheap it would be!?

One pack $1.79 at the first website I visited. (For 2oz)

Lots of different colors and you can blend them.

2lbs of white or 1.75lbs of "terracotta" is about $10.

Not sure how much one 2oz pack could make- I guess depends on how thin you make the walls of your cave...

05-01-2009, 4:55 PM
I just did a search, and found this excerpt from wetwebmedia (http://www.wetwebmedia.com/FWSubWebIndex/fwaquascapfaqs.htm):

Making decorations for freshwater tank (1/23/04)
Dear WetWeb crew--
<Hi! Ananda here tonight...>
Hi, I read your site everyday, and haven’t been able to find my answer in the Google search.
<Check the forums, too -- http://wetwebfotos.com/talk (http://wetwebfotos.com/talk) ... cause I've talked about this on the forums! :-) >
I want to make my own decorations for a FW tank. The pieces I plan will be fairly large.
I’ve done mold making/casting, but does the poly-resin have to be FDA approved?
<It's definitely safer that way. You need to get a resin that won't leach *anything* into the water.>
Can you tell me a specific type (brand) of material can safely be used in tanks?
<I've shied away from using resins because I'm not sure the stuff I have on hand is tank-safe. If you do find out a specific brand, I would be *very* interested in hearing about it!>
What about cured sculpey; plaster, or concrete after sealing?
<Sculpey: Once you bake it, it's safe. I've been using that in my tanks (both freshwater and brackish) for two years. You can use acrylic matte medium as a glue to attach gravel etc. to a base and create your own fake plants using silk plants from the craft store. 100% pure silicone (from the hardware store) works as a glue, also; just make sure you get the kind that has nothing but silicone in it. Plaster or concrete: Both of these will send the pH through the roof if they aren't totally sealed. I'd be very, very careful. Check out the forums for topics about "gravelcrete" or "gravocrete" and "aragocrete" for comments about using cement-based substances in tanks. You have to cure them for weeks before they're safe to put in the tank.>
What sealant is safe to use?
<For Sculpey, I use acrylic media (the stuff that's just the acrylic polymer). I haven't tried either plaster or concrete.>
Are regular acrylic craft paints safe to use?
<They should be, if they're well-sealed or worked into the Sculpey and the baked pieces sealed.>
I read the “bioassay” article, and everything archived about decorations, but was hoping you might have a specific type of material that would be a good place to start experimenting.
<Hunt out a ceramics shop. Poured ceramics, once fired and glazed, are safe in the tank. I haven't done ceramics in years, but I suspect they may have matte-finish glazes by now.>
Thanks for your time and great advice!
<You're quite welcome, and I'd love to know what you come up with! --Ananda>I guess two years without problems would suggest its safe. I'd like to find a bit more info, but I haven't come across anything else yet.

Edit: A bit more searching and I found this:http://www.plantedtank.net/forums/diy/82228-trying-out-sculpey-caves.html
This person's post seems to summarize the small bit of info I've been able to find on the clays.

I use super sculpey quite a bit, so I could whip up something and test it out in a container of snails. I've been wanting to get into making aquarium decorations for a while now anyways.

05-01-2009, 5:44 PM
Yes... this looks like it really might work... I'm off to Michaels to see if they have any... Not sure what I'm going to make for caves... I'll see what inspires me! ;)

Thank you!

05-01-2009, 6:25 PM
Just don't get original sculpey, I've had a lot of trouble with it crumbling. The super sculpey, however, is pretty sturdy. I had a 1" figurine I experimented with, and it took about 7 times bouncing it off the floor to finally break it.

05-05-2009, 6:31 AM
I bought some of the stuff but haven't had a chance to use it yet.

I have however received a reply (finally) from Sculpey:

Thank you for contacting Polyform Products Company. Our clays do not contain any toxins, heavy metals or copper. While Sculpey is non-toxic, we have not done any testing on it in aquariums. I would recommend visiting message boards and forums to find out what others have experienced. I have not heard of any problems, but I am not involved in the aquarium community. There are some glazes that can be applied to Sculpey to make it water resistant, but as these glazes area made by different companies, I am not sure of their effect on fish. Sculpey can be placed in water without a glaze, but over time a whitish film may develop on the surface. This film can be wiped off with a cloth. I am sorry I do not have additional information for you.

If there is anything else I can help you with, please contact me again.