Here's what id say. I say take the pleco back, because most get huge, and you'd need like 200 gal
. For. A good stock for a 5 gal
would be a betta (male or female) and some shrimp, you could 8 or so, as they have almost no bioload, and there great at cleaning things up. Heck you could even get a goofy looking snail with all that
You also may want to read about the tank cycle process, (fishless cycling is the most favored here) but if you absolutley have to keep a fish in there from the start check out fish in cycling. (I will warn you, however, that the shrimp and snail may not survive a fish in cycling, and the betta, or even the pleco you have now might not 100% either :/ )
One last thing, for plants mario moss could be done just with window light, or ambient room lighting, but for most plants, you will need to ugrade the lighting to something more powerful
(its always fun getting new gadgets for your tanks
I hope you keep us posted, and just so you know everyone here loves pics
Good luck on the tank, and have fun.