I have 2 HOB filters with bio wheels. When I do my weekly 30% water change,which takes about an hour,am I hurting my bacteria bed? The bio wheels have no water running over them during this time and my bio filters inside are only half covered with water.

As soon as you turn filters off bacterial will start dying of oxygen depletion. However, as long as you don't turn them on for too long, you will have plenty left to do the job they are there for. After a large water change when you're filters have been turned off, I would suggest not feeding too much for a couple of days, this should reduce the amount of waste going into the water.

An hour is quite a long time, but it's certainly not going to cause catastrophic damage to a biological filter. The worst thing you can do is let your media dry out, this will kill them, so make sure it always stays wet, even if the filters are not running. I often turn my filters off for an hour and haven't suffered any major problems

keeping them covered with water is important and I would never let them become dried out for an hour. they will be ok with the water not running but to be honest i think you are pushing it with an hr. 30mins would be a better time to me but i am sure other member have had there filter out for a hr or more and said its been ok. I moved house and had mine out for a longer time but not uncovered with water too. any way you can keep it covered I would do it.

pretty much the same as OFL said )))) snap.)

I dont know about HOB's but I vaguely remember a post about this a long time ago. The advice given was to put the wheels in the tank while doing the maintanence to stop the wheels drying out

well for me personally generally i dont even turn my filter off when i do filter work on a HOB, i just lift the top cover and pull out the cartridges and put in new ones. i only turn the filter off if i do more than a 50% waterchange in my 55 for watever reason that may be, and only then because thats about the max you can drop the waterlevel in the tank and have the filter still function without siphoning itself back into the tank. damn that gravity lol.

this where my DIY bio filter plays important role. remember that series of
empty mineral water plastic, whenever i cleaned the first one, the next
cartridge becomes the pre-filter and the one i cleaned will be in the last
stage. all connections are slip-on connect, thus easy to dismantle