i began one year ago with one and moved over the tank until one powerhead almost killed but survived and right now have 4,the love t5 and mines do not like direct light.the flow is very important too because direct flow stress them well we must learn of our experiences i had to protect the nemms from the power heads ejm ko'ralias that ,now i am using others protected to avoid accidents,i feed mines with shrimps once a week buth one solution to my moving nems could be the basket