Where do people get big rocks for their aquarium?And how do you make it safe?
You can buy large rocks (depending on how large you're talking about) at any just about any sod and stone supply company. Don't tell me that those rocks are not safe to use as I have an 8,000 gallon Koi pond that is lined with 6 ton of them. The pond has been up and running for 13 years. Yes, you can hand choose the rocks you want. All I did was rinse them off when the pond was first being built.
Pee Tee is correct. To make sure (or as close to sure you can get) your fish are not harmed and are as healthy as possible the pet store is the way to go. But their selection is very limited so I understand the appeal of purchasing rocks from a landscaper or Home Depot or what have you. If you do decide to do the latter, scrub the rock hard with a scrub brush and water. Then soak it in aquarium salt water for at least an hour afterwards. Rinse and scrub again. I've had success with this so far. Pet store is still your safest option.
Many aquarium shops sell rocks for fish tanks. If you want a lot of rocks, a better place to look for them is places that sell rocks, gravel, sand, and so forth for landscaping and construction. They will be much cheaper there, and you may have a wider selection. You can also buy them online, but the shipping cost for large rocks is prohibitive, unless you're buying at least a whole truckload of them. To be suitable for aquarium use, the rocks just need to be hard enough not to come apart when they are immersed in water for a long time. Some rocks, mostly those that contain calcium carbonate (like limestone, dolomite, tuffa, and sea shells), will buffer the water (make it harder and raise the pH). This is good if you are keeping a hard-water tank (like for Rift Lake cichlids and some other freshwater fish) or a marine or brackish tank, but it's bad for a softwater tank. You can test rocks by getting some acid (geologists use hydrochloric acid, but strong vinegar will also work) and dripping a few drops onto the rock. Calcareous rocks (those that buffer the water) will fizz (make small bubbles) when acid is applied. If the rock doesn't fizz, it won't buffer the water. To prepare rocks for aquarium use, all you have to do is wash the dirt off of them. It's not necessary to boil them or otherwise sterilize them. Unless the rocks have just come out of a lake or river and are still wet, they won't have anything on them that can affect fish. Be sure to place rocks directly on the bottom of the tank (not on top of sand or gravel). Many fish will dig under, them, and this can make the rocks fall, which can crack the aquarium glass, causing an empty tank, a flooded room, and dead fish.
