Thanks for all of the replies!
I see from the various responses that I need to give more details about this tank.
First, I misspoke about the size...its a 150.
Second, the tank has been set up for about 5 years. The substrate is a mixture of peat moss, cactus mulch, and sand which I haven't changed at all.
The water is pure RO that I reconstitute with salt mix to a 100-110 ppm level.
The lighting is direct sunlight for most of the day, with dappled sunlight because of a large tree during noontime.
I use CO2 injection via a converted calcium reactor and a pH controller. The pH is between 6.2 and 6.4. I check the controller probe monthly. Oh, and the probe is in the tank, not the CO2 reactor.
I already have about 20 otocinclus because that is all the LFS had. I had seen one response that recommended 1 oto per 5 gallons (and another elsewhere on the internet that recommended 1/gallon!). I didn't intend to follow THAT recommendation! 150 of just about ANYTHING seemed too much.
The otos seem to be doing very well, and as far as I can tell, I haven't lost any. It is difficult to tell because they cruise in a school much of the time. I feed lots of greens, besides quite a bit of algae in the tank, because there are a number of Pelvicachromis pulcher that I feed lots of greens, mostly spinach and spirulina algae. I feed a variety of food because there are also cardinal and Congo tetras, including cichlid flakes, live daphnia and live mosquito larvae. There were large number of guppies in the tank, but most now reside at the LFS.
I fertilize using the EI method, which seems to be working just fine so far. I mix the various chemicals dry which I store in a tupperware container and dose daily.
Thanks for the heads up about the SAE. I will avoid them.
Thank you all for the responses!
Mike