Like I said before...critters are only really effective when mixed with good algae fighting husbandry.
There is no question a handful .. 6-8 Nerite snails will keep green algae on plants under control without harming the plants. They also will not reproduce in fw which is a plus for non snail lovers. They are NitrAte sensitive so water changes and moderate NitrAte levels are required.
IME even the so called plant safe varieties of plecos sooner or later are seduced by the dark side causing major problems in a planted tank.
Algae on the glass (plastic)
1. Diatoms...small brown circles, very hard, in your case a plastic scraper. Ottos will eat it
2. Green spot algae..same as 1
3. Green Dust algae...the algae that coats your glass/plastic tank walls that you are continually trying to wipe off once or twice a week.
This nuisance algae is a Zoospore. When you scrape it or wipe it, it actually swims around in the tank for 10 - 15 minutes and then begins to reattach itself to the glass.
Just recently a cure has been discovered. The cure, however, requires a little patience.
You simply let the Zoospore run out its cycle. Let it grow on the glass and form a thick coating, sometimes you cannot see through the glass. It takes about two weeks and lot of whining from others in the house, but at that point the algae has changed its physical structure and will literally fall off the glass in sheets with a light scrape.
You then vacuum the stuff off the bottom, do a water change and you will not see it again for a long time. I just recently had an outbreak, have not seen it for years, and found the technique works great. I have seen reports that some folks have had to repeat it a month later, but then it was gone.
Jay
