Let me point out that the so called "vinegar test" is NOT suitable for testing for the presence of calcium carbonate. Acetic acid reacts with lots of other stuff beside CaCO3 and is far to weak to give accurate, reliable results Odds are if you feel the need to test it, you probably shouldn't use it. (See The Number One Rule, below). Better to use Murietic Acid (Swimming Pool Acid), or even better, the off the shelf aquarium product called "pH Down".
The number one rule here is "When in doubt, leave it out!"
Here is a very generalized "Is it safe?" list: (Mind you this is for aquatic use.)
Clear Glass- OK as long as no pointy or sharp edges. Dangerous if easily broken.
Leaded glass, Crystal, etc- NO, heavy metals used in fabrication can poison your critters
Colored Glass- Some are safe, some are not. Refer to the number one rule.
Plastics- This is a tricky one. Depending on what you read and who you talk to, many are unsafe. Many are perfectly safe. There are so many types of plastics I could probably write a long boring book on the subject and still be unable to give you a definitive answer. I will cover a few of the common ones that I personally use without issue: PVC, CPVC, Plexiglas, Lexan (there is a bit of argument on some of these also. Use the forum search function for more details)
China, Bone China- Bad idea. Many contain heavy metals that can leach out, even if glazed
Porcelain- Glazed, yes if rated for food use. Unglazed, no. Same rules as clear glass apply.
Metals, any- No, no no no no. Even if they are painted, powder coated, or sealed.
terracotta - Perfectly safe if boiled for a few hours as long as it is the standard, unglazed, red-orange colored stuff and is fired. (think flower pots) Use caution, some "terracotta" products from Mexico contain high amounts of lead as a coloring agent, as they are not real terracotta.
Red brick- Most are perfectly safe, beware of bricks that have been treated to give them "old" colors. Boil as you would terracotta or rock
Rock, Stone, etc- Really need to get moving on the CC articles on the topic. This is a vast subject. use the forum search function for details.
Also keep in mind the chemistry of your source water plays a huge part. For instance, if you have very hard water, limestone is safe to use. If you have soft water (soft as in low pH), or worse your water comes to you through a water softener (as in the Ca has been replaced with N), don't even think about it.
