New tank won't stay clear, help!!

I just got this 20L about a month and a half ago, I did a 25% water change, half water change and a complete water change and it still keeps going green?? There's 2 amazon swords and 4 Anubias, along with a small piece of driftwood I picked up from petco. Could the wood be the problem? I didn't think I'd need a full plant set up with CO2 with the few plants, considering my 10g is thriving with a sword and a handful of anubias. Someone help!!

here's the tank