Firegirl,
Though TheMadNucleus is correct that algae flourishes in nutrient-rich environments, there is seldom an aquarium that doesn't experience this diatom algae to an extent. I've got perhaps the best example of one that doesn't (my other 2 tanks do have other types of algae), and here's my recipe for success:
---1-2 otos (Otocinclus spp., usually Otocinclus vittatus or affinus), a small suckermouth catfish of the family Loricariidae.
---Low-light, fast-growing plants such as Hygros (Hygrophila polysperma) and Hornwort that can outcompete algae for nutrients.
You tend only to find this type of diatomacaeous algae in low-light tanks (i.e. under 2 watts of light per gallon), and I think you'll find that healthy otos are the best solution by far. A distant second are bristlenose plecos (Ancistrus spp.). Siamese Algae Eaters are great for planted tanks with high light and beard or hair algae, but are less effective on this sort of algae, Clueless.