I am planning to try to move into the planted aquarium world. (slowly).

That's possible. Just add a few low-light plants, like Anubias, java fern,
java moss. They don't need special substrates or lighting.

If you want to grow plants that need higher light, it's kind of hard to start
slow. You have to start out planted heavily, to keep the extra light from
generating an algae plague.

I have a nice thick layer of fine
gravel, so I don't want to dig it out and throw it away and replace with
flourite, which might be ideal. Is realistically possible to add laterite
to my gravel? I know it is suppose to be on the bottom layer. Can I do
that without emptying my entire tank?

Yes. You can add laterite balls to your substrate, near the roots of the
plants. There are also some commercial products on the market, meant to
refresh old laterite substrates. Cones, tablets, etc., of laterite, that you
just stick in the gravel.

However, most low-light plants don't need special substrates. And if your tank
has been set up for a long time, it may be fine as it is. A lot of plants will
grow fine in old gravel, which tends to be rich in nutrients.

My other question is can you have a planted tank with a large (not giant)
common pleco? They tend to plow things over. It is a 55 gallon tank.

It might be hard to grow low, delicate lawns with large fish like plecos in the
tank. And they sometimes scrape broad leaves like Amazon swords too close.
But a lot of people keep plecos in planted tanks successfully.


Leigh

http://www.fortunecity.com/lavender/halloween/881/