what's aquarium safe?

[Prometheus]

hi, im thinking about lowering the water level in my 29 gallon and making it into a paludarium. i don't want to silicone glass plates to form a water proof base for the land area so i thought id just build an island up out of rocks and/or driftwood. so, my questions are:

1. how do i know if a rock is safe for my aquarium and won't kill my tetras or rainbows? if i pick some up from a reputable local fish store should i be able to trust that it is fish safe or are there different types of rocks that might change the hardness or other water parameters despite the fact that it is supposedly good for aquarium use according to said lfs?

2. since im building the island up with rock/wood i am planning on needing to use pots to put my plants in (im planning on the pots being imbedded and hidden from view when finished). are terra cota pots okay? what other suggestions would you make?

3. my island plants will need soil, right? i suppose i could use sponges and allow them to grow down into the water. what kind of potting soil is safe for aquariums?

4. i have an old piece of driftwood that has been outside in the elements for about a year or two. it has washed out (its mopani wood i believe) and is not the color it used to be. i guess hot summers and snowy winters will do that to a piece of wood. what are you thoughts in regards to whether or not it can be salvaged and used again? not being able to see it for yourself is there something i can do to it like soak it in a bucket of hot water or something?

 

[Fat Homer]

1. certain rocks will change the parameters hardness etc

2. Terra Cota pots may leech stuff? you could always use the plastic ones instead?

3. For my paludarium, both land and water area i use ADA Amazonia Soil

IF not one else has answered by the time i'm off work, i'll try and go into a little more detail...

 

[Redearsunfish]

Why would terra Cotta pots be unsafe? What would they leach?

 

[kamikaziechameleon]

Generally the more porus the rock the more it affect ph. Look out for slag/flag rock and limestone since they can have other metals in them that you don't want in a smaller tank like that. But generally I rinse rocks and then drop them in my tanks. I would say 99 percent of my stone is field stone or landscape stones since they are cheapest/free. Texas holey rock and stuff will buffer your ph up but not much compared to some good sediment bringing that ph right back down so don't worry. I have use flag stone but you just gotta be careful with it and without a test tank I'd stay away.