Hi my 35 gallon tank has an undergravel filter(i like to keep it in just for the aeration really)and a fluval 3 filter,one day i found the filter had fallen off its succker holder-suckers arent strong at all.so no i have suckered it so the base is almost on the gravel bed-incase it falls again i dont want it to hurt a fish.will that be ok?its still sucking up fine but i wondered if itd be less effieciant without the water flow at the tank top,as i say i do have airstones and bubbles also for airing the water top.any advice gratefully recieved♥

That happened to me once with a Fluval 3plus.I suspect it isn't as efficient laying on the bottom as in its normal position.As you have an airstone I suggest reattaching it to its holder and having the filter stand upright on the bottom of the tank.Its not ideal but with your airstones it should be ok.
I currently have a fluval 4plus sitting on the bottom upright attached to its holder due to the large plec in the tank.He already knocks the heater down.

Thanks blue..i bought a whole new holder for the fluval(aparantley the suckers are famous for being rubbish!)and ive popped it back at the top..im a bit nervous incase it falls again but so far so good.i wish they still made the hook on holders.