I keep a group of otos in 6 of my tanks and they are great little fish, always working and always so full of personality.
I find that my group always eagerly take algae tablets, particularly ones with spirulina in as well. They have also been quite happy to take home made duck weed and spirulina food that I've made in the past when I followed a video recipe on YouTube.
Something else I tried with some success was taking a sealed jar of their tank water and putting in direct sunlight to allow algae to grow, then emptying the water out and placing the jar into the tank.
I find that my group always eagerly take algae tablets, particularly ones with spirulina in as well. They have also been quite happy to take home made duck weed and spirulina food that I've made in the past when I followed a video recipe on YouTube.
Something else I tried with some success was taking a sealed jar of their tank water and putting in direct sunlight to allow algae to grow, then emptying the water out and placing the jar into the tank.