Possible new 24g Dwarf Puffer AquaPod setup questions

Hello,
I'm looking into a new tank for the wife, she loves lil dwarf puffers, and we haven't wanted to put them into our 55g community...

I've been doing a bunch of research for days, and I'm going to go w/ a 24g Aquapod (was that or a 29g BioCube, both had similar reviews, and can get the Aquapod from Drs.F&S for less than $200 shipped now...)

I'm going to do 4 DP's, 3 Kuhli loaches, 3-4 Oto's, and a bunch of cherry & amano shrimp (this seems to be a fine combination from www.dwarfpuffer.com forums)

I'm going to do it planted tank of course....

Question is, I'm trying to figure out how to be cheap on the CO2...I mean I have a 10lb tank and regulator and pH controller on my 55g, and it works awesome, no real algae problems (using EI, and UV sterilizer)

I'm thinking of doing Aquasoil and powersand for substrates, I'm reading this is going to help keep the pH down...the Aquapod comes w/ 2.6watts/gallon, and I'll be doing a 1/2 dose of EI that I'm doing now...but, I really don't want to spend another $100-250 for a CO2 system (no I can't link the current one to the new one, too far apart in the house and the solenoid is controlled by the pH controller in the 55g)...so, could I get off easy by just using Excel? I know its not a real CO2 system...but, I was thinking that if I had the good substrate , and had 2.4w/g for 6-8 hours/day, and *only* used very hardy plants, and had Oto's and Amanos & cherries, that I could get away w/o doing CO2?

I mean, I know PB has a few tanks w/o CO2, and I'm assuming that's what the low-tech tanks are (sorry, too tired now to keep reading if this is a easy question over there...)....would I just be asking for trouble w/ algae using Excel instead of a real CO2 system?