Growing Algae for Otocinclus

[aquahead1]

I'm starting to farm aquarium algae. I've started out with tank water, a little bit of grazing block enriched with algae, all submerging a rock inside a bowl, which is inside a bag. Is this algae I'm growing safe for the Otos? I was going to get some small algae covered rocks from the creek that's like 50 feet away from my house, but I don't think that's the algae I want. The rock I'm growing algae on is a smooth, fake plastic rock. The Otos have sucked on it before, and I want them to feed on some algae to make them seem more secure. Is this the right method of growing Otocinclus algae?

[Lady Hobbs]

Stick some low light plants in the tank and they will feed off that.
I also offer up a slice of cucumber now and then.