Algae on plants

[fishb0ne]

I've got some plants that I've potted and am actually keeping in the outdoor pond over the summer. I've re-potted them yesterday afternoon and this morning the pots had a bunch of green string algae on them. They've been in the pond for about 2 months now and have grown new roots, new leaves so they seem to be doing OK. Every now and then I try my best to rub off the algae off the leaves.

How much is too much? Is there a point where the plants get choked off? They're in 16 inches of moving water and are getting plenty of sunshine. I'm guessing since they're growing fine to just leave them be?

 

[Purrbox]

Are there any fish in the pond? Do you dose fertilizers at all? Have you tested the water to check Nitrate and Phosphate levels?

 

[fishb0ne]

No dosing of fertilizer at all. There are a bunch of koy fish, if what you're about to ask is do I have a slight algae problem then the answer is yes. There are fish and there are also some plants but unfortuantely not enough and also the sump pump is a 5k gallon capacity, the tank is 6k and it only runs during the day from 7AM to 11PM.
I checked today and the plants were covered in green algae, I aggitated the water a bit and it cleared right up. They seem OK for now, we have been getting a decent amount of rain too for the past week.
Here's a topic about the pond:
http://www.aquariumadvice.com/viewtopic.php?p=781411
There's a link to a slideshow at the very bottom of my original post there. In pic 16 follow the waterfall all the way up. In that large container which also houses the bio media are the plants housed. Although it looks like it in this pic, it's actually in the background so it's not covered by any plants. Plenty of direct, unobstructed sunlight all day. Here's the pic I'm talking about
http://new.photos.yahoo.com/fishb0nex/album/576460762388229827/photo/294928804215179659/15