Custom Ceramics in Aquarium

[Narwhal]

A few years ago I made some ceramic rocks for my cichlids out of a terra cotta clay (what they make pots out of) They have done well with my fish, the semi-porous surface allows for more bacteria to colonize it. I recently took a ceramics class and made some stoneware cichlid stones. They are high fire. However, I found out the make up them
Kaolin (clay) 25-65%
Crystaline Silica - quartz 10-25%
Silicon dioxide <5%
Feldspar <2%
Brown Iron Oxide <2%
Titanium Dioxide <2%
Kyanite <2%
Pyrite <2%
The Pyrite is what concerns me, as it breaks down into sulfuric acid, it will lower the pH and free up the hard metals in the water.
I have had them soaking for a few weeks now, but the pH is yet to drop.

 

[Imsobored152]

Are these glazed? Not that I know the answer if they are or arent, but might help someone else's answer.

 

[kewpiefishypewpie]

I'd be interested to know as well as I've seen some tanks, of very esteemed keepers, whom have painted and glazed pots in their aquariums to no ill effect.

 

[Narwhal]

both types are unglazed
my guess is it should be fine, most forum posts I have seen is that a small amount of pyrite should have little effect, but I will let them sit in regular water for a few more weeks.

 

[Athletic_Amph]

I'd like to think the type of glaze would be the determining factor? When I took ceramics in school, there were certain glazes that were "food safe" and capable of being used on dishes, pots, my beer mug, etc... those would probably be more safe for aquarium décor, no?

 

[Narwhal]

pretty much all ceramic still has an unglazed portion, they would stick to the shelf if glazed all the way. I have a very old ceramic tiki house that appears to have been made for candles, the part that touches the gravel is unglazed (that has been in tanks for 10 years)

 

[GamerChick5567]

As long as they aren't painted on outside of the glaze or flaking a lot when you pre soak them or whatnot I say go for it, I always keep at least some type of ceramics in my tanks, with no ill effects.

 

[Narwhal]

Terra cotta has been used in tanks for a while, people use pots to breed fish, and some terra cotta is even made into fish caves (should be good without glaze, or a food safe glaze)
my cichlids stones on the other hand are made from a different clay called Rod's Bod from Laguna clay (http://www.lagunaclay.com/clays/western/wc823.php) they do not have glaze as I like the sandy texture and rocky look, that would be less natural looking if covered by a glaze (which is smooth glass) My main question is how long for the small amount of pyrite to become HCl, so I can simply wash them and they will be inert? also has anybody heard about any of the other minerals in the clay from the first post as being toxic?
As I said they are probably safe as the minerals in the clay each make up less than 2% of the object.