First large tank and too many fish...

[jelisalyn89]

**check out the picture lower in this post - fish mesmorized by a fake plant - thought it was funny... theyve been staring at it for over 3 hours...)

A friend of mine ended up with too many fish for her tank, so she asked if I would be able to take about 6 of them. I had a 20 gallon tank that we use to use so I said I would take them. I got the tank set up, bought them rocks and a filter good for up to 30 gallons. She handed me a bag of 13 fish... which I believe is way too many from the information I've been reading. I'm wondering if there's anything I can do to make this work? What about an algae eater? cleaning the water frequently enough? Any suggestions? I've never had more than one goldfish in a smaller tank... and I keep reading about bubbles - is that something I should have as well?

oh, and I think they are "commons" from the pictures I've been looking at ... and the poop is starting already...
thanks a lot.