I tried using a DIY system for my 55 gallon tank. It failed miserably. If you have a very small tank (under 10 gal), it might work.
I have a 55 gallon tank and use a full presurized system. I can usually go about 4 months between refills on my 5 pound CO2 tank. For smaller tanks, a 5# tank may be more than you need. There are also systems that use paintball tanks if you have someone locally who refills them. Many paintball enthusiasts have begun using pressurized air tanks rather than CO2, so it might not be easy finding someone to refill your paintball tanks.
I have no experience with the UNS system sold by Buceplant, One thing I like about it is that it is a dual stage regulator. Some people go with single stage regulators to save money, but if you are using a paintball tank, that might not be a good idea. When the tank goes empty, it is possible you can get a end of tank release of extra CO2 which could be a problem in a small tank. Thus, a dual-stage, or even a triple stage is safer.
I have been using an F-zone Professional dual-stage regulator for the past two years. It comes with two needle valves and bubble counters you you could use it with a second tank should you install one later. The regulator and needle valve have been rock solid over those two years. I might need to make a slight adjustment to the valve when installing a new tank of CO2, but generally that has not even been required. It is a set it and forget it system. It comes with a built in solenoid valve which you can connect to a timer so it will only run when the lights are on. I turn mine on about 1 hour before the lights come on and then turn it off about 1 hour before the lights go out to get maximum effect from the CO2 without waste. The solenoid uses 12V DC which is safer than a 110V AC solenoid.