For your betta tank, it looks like it's cycled according to your numbers. If you swap out the entire gravel base for a new one, you may go through another mini cycle since you'll be tossing out most of your friendly bacteria. The common practice is to swap out your gravel a third or half at a time, giving the new stuff time to build up the friendlies. Eco-Complete seems to be the substrate of choice for people wanting to plant, though I've got plants in my Pool Filter Sand and they seem quite happy with some root tabs and pre-mixed fertilizer.
You have plenty of light in your betta tank in terms of Watts Per Gallon, though I'd suspect it's probably sub 6500k color temperature on the tube you've got installed. If it's a standard sized tube, you might have luck replacing the tube with a tube suitable for plants. Any tube that's rated at 6500K to 10000K will work fine. You could buy these at pet stores for $10-20 or at a hardware / lighting store for $2-$5, if you have such a beast in your area.
For your minnow tank, you COULD buy a whole new light strip, or if the incandescent sockets are of a standard size, you could just buy CF
bulbs to screw in. In a worst case scenario, if you're handy just retrofit into the existing one if you want to go to fluorescent. What I did, though it's kind of a hack, was to empty the guts out of the plastic shell of the light strip. Then I bought some rubber exterior light bulb sockets (for standard lightbulbs), fastened them securely with epoxy up inside the old light strip casing, wired them all up in parallel. Then I bought some 6500k 11W Compact Fluorescent light bulbs (I managed to fit 8 sockets in total in my strip for the 29g) and screwed them into the new sockets. When I plugged that bad-boy in, it looked like a whole new tank, and now I'm constantly trimming back new growth.
If you go this route, ensure you use heavy enough wiring, I'd recommend 12awg house wiring, to be safe. I didn't have enough room to use marette connectors (those wire nuts that you twist on to ensure the connection is solid) so I ended up soldering all my connections and double taping them. I didn't have a WHOLE lot of room to play with, simply because I was trying to fit 8 u-shaped lightbulbs into my 24" long hood.
Of course, I was limited in wattage by the local selection of CF
bulbs, as well. If you can, try to find higher wattage bulbs, but make sure they're in the 6500-10000k color range. A bulb outside that range will light the tank, but won't be of much use to the plants.
I wouldn't worry about CO2
until you have well over 2 watts per gallon, and/or start experiencing problems with algae blooms. I've got slightly over 2WPG, taking restrike into account, and I figure I probably SHOULD be running CO2
to judge by other's comments, but I haven't ever seen a speck of algae in my tank. I attribute that to the fact that I don't overfeed, and I have a bubble stick running off a standard air pump that helps to keep CO2
at atmopsheric levels.
Unless you want super fast growth, or a jungle like tank, I don't think you need CO2
for beginner plants or a sparsely planted tank. The biggest thing CO2
does for you in these situations is helps keep algae in check, because once the CO2
level drops in a tank level, plants stop using up their nutrients because they're choked, but algae which doesn't need CO2
will have a field day on all those free nutrients. Keeping a bubble wand running all the time will keep the CO2
from dropping out completely, though there's little enough in atmospheric air (about a third of a tenth of a percent of air is CO2
) so it won't do THAT much for plant growth.
That's all I've got. If anyone knows what kind of lawn/carpet plants he could grow, I'd be happy to hear, too, as I'm having terrible luck sourcing some sort of ground cover plants myself.