For quite some time now I have been growing Ulva intestinalis in my L2 Rev3. I stumbled on this algae quite by chance a few years ago when I was sent some from the Island of Guernsey situated between the UK and France. When it was sent to me it was sent as just a local algae that was growing on a guys ATS screen. It The Ulva was presumed to have arrived as the guy used local seawater in his aquarium and the seeds from it must have been brought in, in the water. This Ulva obviously found the conditions in his waterfall ATS to be ideal for colonisation and growth. Ulva intestinalis is found in many oceans around the world, in rock pools and often attached to stones on the beach. This Ulva is very tolerant of salinity and can be found where rivers meet the sea. I have found it in marinas and on the seashore. Ulva does like flow and does best in a constant flow of water. Ulva intestinalis also likes light as it is most often found at or close to the surface. When Ulva is seeded on a waterfall ATS it will grow at a phenomenal rate, up to 2" plus in 24 hours I have found given plenty of light. This Ulva certainly out grew GHA on my screen. Seeding Ulva is best done with a bit of modification to the screen to speed up colonizing of the screen. I may write about that another time but I have posted a "how to" on Facebook forums and various .com forums in the past. Ulva intestinalis is an amazing algae and the only drawback is that some report it can invalid the DT. However many algae eating fish will eat it and in fact many feed the harvested Ulva to their tangs etc. The following photos are of 5 days growth of Ulva.