Unfortunatly most suction cups don't suck, at least not for long The micro algae bacteria film, etc always seems to defeat them in short order. I would recommend getting some acrylic scrap and making your own hangers by forming brackets from acrylic strips. You can use Nylon screws to tighten or adjust them and nylon zip ties are hand for attaching powerheads to said bracket. Good luck
First it depends on the suction cups you are talking about, most are not very good but maxijets can work well as long as you follow a few simple
procedures. First make sure the surface is cleaned right before you apply the suction cup so there is nothing bewteen the suction cup but glass or acrylic . You will have to follow up and double check the suction cup and press down on them for the next two days to make sure all the air is released. At this point you should be set until you have to take them out to be cleaned. I would reccommend cleaning every 3-6 months using a small bucket and vinegar solution. Remember to replace the suction cups at least every 2 years due to the fact that the rubber breaks down. I just did a full replacement of suction cups for all my powerheads and I think I paid about 50 cents per cup.
Yup... the magnetic powerhead holders are great. They also work on my Visi-Therm heaters - just hot glue the heater holder to the magnetic powerhead holder. Been running that way for a couple months and the magnet doesn't effect the thermostat at all.