Green Mold inside soil container

I just started a seedling in a soil medium (FFOF). The container is a one gallon milk jug. The seedling is three weeks in and doing fine. However the milk jug is opaque and must have let in enough light for some kind of green mold or something like that to start growing, as on the sides (inside of the jug) there is something green growing. There is nothing growing on top of the soil, so I'm thinking whatever it is, it can't handle either direct light or fresh air (possibly both). So far the plant seems OK, and it doesn't seem to be having effect on the pH balance (From checking the run off). If it's some kind of mildew, will Capstan get rid of it? I have a paper sleeve taped around the jug to see if that helps get rid of it. Any ideas?

probably just algae because of light hitting the moisture in the soil, same as you get on the inside of a fishtank. make sure NO light gets to it, gaffa tape or similar should stop it it increasing.

After I started my air pump in my h2o I noticed a green ring from my ferts around the rim of the bucket. kinda looks like algae or mold but it's not. maybe that's what happened here?

dura72, I took your advice and 'light sealed' the entire container with duct tape. I'll peel some of back and see if it helped in a week or two.... the plumber, I don't think it's any kind of nute problem as I'm using Fox Farm Ocean Forest, and haven't used any nutes on it yet (the seedling have only been in the soil for 3 weeks). Thanks for the replies, guys.

I read here that some growers are using cinnamon to prevent mold. How much should I use and how should I use it? Also hydrogen peroxide was mentioned, how is that used?

Update, I blacked out the light with the tape, like I said above, and it killed the green stuff, after about 10 days!!!