For this Instructable, the first I've done in a while, I will be showing you how to use an old liquor bottle to create a stylish, nearly free, CO2 gas generator for a planted aquarium. The aquarium I'm doing this on is a small Fluval Spec V, this will work for larger aquariums however, just up the bottle size and CO2 ingredients accordingly. This should run about 2 weeks before needing to mix up another batch of the CO2 creating ingredients.
What you need:
Suggested but not required for this build, especially if you intend to keep fish with your planted tank, is a CO2 test kit. These are cheap, you can pick one up at your local fish store, or you can pick one up on Amazon for 15 bucks. http://amzn.com/B0052M9886 If your CO2 levels rise outside of safe levels, just cut back on the CO2 ingredients detailed in this instructable, use a control valve, or consider only running it during the day by installing a common air hose regulator available for a few cents at the fish store and cutting it off in the evening, or pull the hose from the bottle if you're around enough to manage that. Plants consume CO2 and put off oxygen during the day offsetting the CO2 being put out, but at night they consume Oxygen... and the combined effect could kill off your fish during the night. There is a lot of literature on the internet about these concepts, and of course a lot of opinions... and a basic understanding of the ecology of a planted aquarium should be obtained before introducing anything new that may kill your critters off.
1 750ml bottle, emptied and completely rinsed out with fresh water (no soap, even trace amounts of soap can kill fish and may impede the CO2 production)
Enough aquarium air hose to reach from the spot you want to place the bottle to the intake on your aquariums filter or outlet of the powerhead
If the lid for your bottle is not already cork like or similarly air tight, a wine bottle cork... usually the same diameter of most liquor bottles will work fine.
A backflow preventer, commonly referred to as a check valve, that is the correct diameter for aquarium air hose. Available for a dollar or two at most aquarium stores near where they sell air pumps and hose.
With this setup I haven't had any issues in this size tank, but it's always important to test water conditions with any aquarium on a regular basis.
In this aquarium, as an FYI, I have the following low light plants and critters:
Plants in Fluval Shrimp Substrate:
Dwarf sword grass
2 Porkchop rasboras
3 Blue rasboras
Zebra nerite snails
The rasboras will eventually outgrow this tank and the bio load will be too great, but I have other tanks to safely transfer them to when the time comes.