With a little brainstorming and taking some great advice that I've read elsewhere, I was able to feed all 4 horses tonight and feel that they had plenty. I ended up placing a shallow plastic dish in the corner of the tank that Navajo and Apache frequent for feedings (held down by a piece of rubble rock). When I went to feed them tonight, I gave them the normal cues...equipment off, tapping on the glass to direct them. It took them NO time at all to find their mysis in the dish, and this GREATLY minimized the number of bristleworms out and about (and for that matter, the amount of excess mysis in the tank). With that being done, Maya was in the same neighborhood as the the new dish, so she got some mysis (she ate about 5-6 pieces). Inca, on the other hand was hanging out in the back of the tank on a plant and got spoon fed. He also ate about 5-6 pieces, which is fine since they're so tiny.
It worked out great, and I will continue to feed my horses in this manner. What a learning experience.
Lisa