I'm not sure what you want in the way of suggestions. I will try to answer the couple of ?? at the end.
Surface agitation keeps the top of the water stirred up and clean. It helps to oxygenate the water. If you only have mild agitation like a small ripple caused by a spraybar it's not a big deal and actually helpful. If you have hang-on-the-back (HOB) filter that caused O2 to go deep into the water then you will force more oxygen in the water and CO2 will come out. If you are trying to infuse CO2 that works against you.
This is the same concept with bio wheels. The expose the water to more O2 which drives the CO2 from the water. Plants need CO2 as a carbon source so it works against you.
I don't know how many watts a 48" tube give out so I can't speak to how much light you have. If your plants are growing well, then you are doing fine.
You black sand is inert if it's plain sand. You will need something to put nutrients in the tank for the plants. You could use plant tabs, liquid or dry ferts.
Here are some links that might give you a nice overview.
http://www.aquatic-plants.org/articles/basics/pages/index.html
http://beginneraquarist.petfish.net/Beginner%20Aquarist/Home.html
http://www.rexgrigg.com/
Surface agitation keeps the top of the water stirred up and clean. It helps to oxygenate the water. If you only have mild agitation like a small ripple caused by a spraybar it's not a big deal and actually helpful. If you have hang-on-the-back (HOB) filter that caused O2 to go deep into the water then you will force more oxygen in the water and CO2 will come out. If you are trying to infuse CO2 that works against you.
This is the same concept with bio wheels. The expose the water to more O2 which drives the CO2 from the water. Plants need CO2 as a carbon source so it works against you.
I don't know how many watts a 48" tube give out so I can't speak to how much light you have. If your plants are growing well, then you are doing fine.
You black sand is inert if it's plain sand. You will need something to put nutrients in the tank for the plants. You could use plant tabs, liquid or dry ferts.
Here are some links that might give you a nice overview.
http://www.aquatic-plants.org/articles/basics/pages/index.html
http://beginneraquarist.petfish.net/Beginner%20Aquarist/Home.html
http://www.rexgrigg.com/
