Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Plant substrates do several things, and not all substrates are equally good at all these things.
While some are enhanced with fertilizers, this is not the main reason to buy a specific substrate.
Over time, the original fertilizers will get used up.
A substrate might be very good at holding the fertilizers in a way that plants can use them. This is called Cationic Exchange Capacity. I would look first for high CEC in any substrate. This stabilizes the available fertilizers so that if the supply is not regular, the plants do not suffer.
A substrate should be fine enough that the roots are willing to cling to it to get some stability. Some substrates are better than others at this. I would look at this as perhaps the third most important factor.
The second most important factor is how it looks to the fish. Many fish prefer a dark substrate. They feel safer, hidden from predators when they are in the shade of a planted stream bank, overhanging roots and so on. A white or light substrate makes the fish think they are out in the open, exposed to birds or other predators. They will often go hide in such a tank.
Other things that might make a substrate acceptable or not would be the sharpness of the particles, especially if you are keeping bottom oriented fish such as Loaches or most Catfish, or fish that dig nests for their babies, like many Cichlids.
Substrate that alters the water chemistry is another item that is very important.
1) High CEC (never mind what fertilizers come with the substrate)
2) Dark (Unless you are keeping fish that prefer light substrate)
3) Proper texture for roots (Of course Java Fern, Anubias and similar plants do not care about this)
4) Other (What is most important for the fish?)
Do not use a substrate intended for Rift Lake fish in a tank where you want to keep soft water fish. Most often the Rift Lake substrates include lime based sands and gravels that will make the water hard and alkaline.
If you still want a white substrate that is neutral in reaction, then look into pool filter sand. This may vary in color, but is a quartz sand, not lime based.