Stocking Ideas/Advice?

[fishdogs]

Sorry this will be a Long one 😕: I currently have a 20G High tank with 3 common mollies and 2 pygmy Cories. I have been going back and forth trying to decide if I should get more pygmy Cories or not as I have bought 2 separate schools of 8. The first round introduced ich to my tank and my water parameters were not ideal (meaning I was using RO water and not remineralizing). The second round slowly died off but I still have 2 living from this batch. I have been using Seachem Equilibrium to remineralize my RO water. 

Water parameters are currently: 

GH: 250

KH: 0

Cl2: 0

NO2: 0

NO3: 0

pH: 6.8

Should I take a chance and get more pygmy Cories (about 6 more) or should I leave it as is and possibly wait for these two to die?

I currently have floating frog bit and a single Anubis nana plant (with hopes of getting more someday). Mostly plastic plants in the tank and they seem to collect algae like crazy. What would eat algae well? I am not sure if I would like to add a nerite snail to the tank as I heard they poop a ridiculous amount. I am not a fan of Otos (tried those before too). 

[Zeaqua]

I’d definitely recommend getting more pygmies, possibly from a different source. They are a lovely fish, but really don’t do well at all in small groups.

[Tony s]

I’d look into getting some Seachem acid and alkalinity buffer to raise your kh numbers. I’d see about getting the kh to at least 80. Kh is what will buffer your water from large ph swings. And you can target the ph you desire by using them together. 
 

I’m thinking your gh is perfect for your mollies but too high for your pigmy’s. Which can be a bit sensitive. 
 

nerites or mysteries would be fine. They’ll eat more algae than produce waste. So net positive.