green algae

[Richgrenfell]

OK,
so i got the diatoms taken care of (otto cats) now green algae seems to be the problem. it has completely covered the cabomba, and it is also on the substrate. I don't want to keep adding fish, so I was wondering if you folks couuld advise me. Is this just a right of passage that the tank needs to go through? I've been raising fish most of my life but this plant stuff is pretty new to me

Rich

 

[Jason]

Cabomba is a very difficult plant and requires a lot of light.
There are algae in tanks all the time, they are competing with plants over ligh and nutrients. They win with plans when concentration of nutrients is high: they have a relativly much bigger surface than plants, they can absorb nutrients faster and grow faster. This creates shade (less light for plants) and an additional advantage over plants. Decaying algae are a source of nutrients for new algae...vicious circle.
To break it: remove as much algae as possible, change water frequently, and, most importantly: introduce fast growing low light plants, they will be removing nutrients from water. Vallisneria spiralis is a good example, also Najas graminea, Java moss. Java fern is excellent, even though does not grow as fast. There are low light Cryptocorynes, too.
Also, newly introduced plants need some time to adjust (2-3 weeks) during which they do not grow and cannot compete with algae. Things might much improve after the acclimatisation period.
You said you didn't want to introduce any new fish, but just in case: bristlenoses (Ancistrus sp.) are very effective algae eaters.