Re: CO2 planted tank options? Very new to this, teach me!
Hi ShortyKiloGryl,
Sounds like you have an interest in CO2

There are some good points shared in this thread. You can overdose CO2 , but I wouldn't let that stop you. You (we) can overdose ANY additive we put in the fishes water, conditioner, ferts, Meds, whatever it is , it can be overdosed.
For a small 5g it would be easy to purchase those $8-10 small bottles of Excel and use that 2-3X a week. We all have done that. Here is some reading to organic carbon Flourish Excel .
http://www.seachem.com/Products/product_pages/FlourishExcel.html
If you are interested in going Compressed CO2 here are some tools for dosing a 5 gallon. I am going to explain this backwards from the fish tank to the compressed bottle. 1st ; a gas defuser. The defuser that would be appropriate would be a CUP DEFUSER. This is basically a small cup turned upside down with an airline (CO2 line) stuck in the top. I will add a picture later of mine. So basically this upside down cup creates and holds a CO2 bubble underwater. Water current rubbing against it defuses little amounts of CO2 into the water. Any type of small CO2 system will work for this application and will last a long time.
Next is airline tubing. You can seek specialized CO2 tubing for this application. I use both airline tubing, and CO2 tubing, both work fine. You can purchase enough of this to put your CO2 tank anywhere you want.
Co2 tank and regulator. For this application you could purchase a nano set up. This type of set up would be small enough to fit easily behind a tank and still have the tank close to the wall. Or installed on the side without it looking bulky. If you think your interest will expand past your 5 gallon nano, or if you dont care about looks, or whatever. You can contemplate a full sized CO2 system. A full on CO2 regulator with solenoid and perhaps a 2.5 pound CO2 tank. This is what I would purchase. You may at some point switch the system to a larger fish tank. You will be able to do this with a full sized system.
Back to dosing a 5 gallon fish tank. The type of defuser I mentioned above needs small amounts of CO2 fed to it. Just enough to fill the upside down cup and hold a bubble. Every once in a while it'll burp and refill. This is what I use in my 9.5 gallon. My CO2 solenoid is on a timer. It clicks on an hour before the lights come on, and clicks off an hour before the lights turn off.
CO2 and PH. CO2 effects PH. Decaying organic matter effects PH. Both these lower PH. Monitors such as PH drop test kits are handy. Buffers such as crushed coral are popular to bring PH levels up in heavily planted tanks, and planted tanks with CO2 injection. All 3 of my planted tanks have crushed coral somewhere in the system.
Cup snagged from hair spay or mousse bottle .