Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Use whatever sand you want and add slow release tablets well buried, and not too many of them.
Coarser sands allow more water movement through the sand, and this will encourage the tablets to release the fertilizer, and it can end up in the water column.
Pool filter sand is very good. All the particles are the same size (usually 20 or 30 mesh) so it does not compact in the tank, and allows good water movement through the substrate. If you have more than one swimming pool supply company near you, look at the different products. Mostly they will be off white. Perhaps with black specs. Looks pretty good, where I want a white substrate.
Play sand is a mix of fines, and can compact. I have heard of people rinsing away the fines, and ending up washing away as much as half the material.
Black Diamond is blasting sand, available at masonry stores (brick, rock, pavers, concrete blocks and related materials). Do some research- the edges might be sharp, and not good for bottom dwelling fish, or any that sift the substrate through their gills. Cories especially may get minute cuts to their barbels, leading to infection.
Sands available in pet stores may suit you, but be sure you check the pricing, and compare to the pool filter sand or black diamond.
The local masonry stores, and places that sell materials in bulk (soil, bark, soil conditioner, rock...) also sell bags of sand in many different grades. The local bagging is Lapis Lustre. The sand in these bags comes in many different sizes from 30 mesh (same as pool filter sand) to a fairly coarse sand labeled 'Aquarium Sand'. It is about 1/8" diameter pieces- verging onto a fine gravel. You might ask about "Kiln Dried Sand" and see what your local stores have.
Some sand may be from a limestone or related parent material. Such sands will add minerals to the water such as calcium, magnesium (raising the GH) and carbonates (raising the KH). These are OK in hard water tanks, but not good for soft water fish.
If you can get a sample (bring a baggie, and look for a broken bag) take it home and test:
Put the sample in a jar of water with a tight lid.
Shake really well.
Q: How cloudy is the water? Does it go away quickly (few minutes to an hour)? This is good.
Now swirl the jar. Not shake. Just as if you had a filter or power head running that blew some water against the sand.
Q: How cloudy is the water? If it clouds just a bit, then it will probably be OK with a quick rinse before using. If it clouds too much with just a small disturbance, then there is probably too many fines in there, and it might keep on clouding the water.
Test GH, KH, TDS, pH of tap water with no sand, then test the jar of sand and water a few hours after mixing, then the next day, then several days later. You make the call about how much change in these parameters is OK for the tank set up you have in mind.