I disagree about algae does not come from under filtering. Amano himself states that if a tank with heavy plant bio mass is under filtered algae will be a problem. I run my lights 12 hours a day or more & algae is not a problem for me at all. I do run twin canisters on a this tank which is only 10 gallons. The water stays very clear & the plants are doing well. I had many early tank problems that were so bad I al most packed it in , until I added a second canister. Now my fish & shrimp are healthy . I would always consiter good flow & filtration & important part of planted tanks being balanced. I use to think less was best. That being said I do get a little algae only on the glass.
Is your light a medium light or low light? 12 hours is a lot, I am curious to know how you could do it successfully without running into hair algae and such?