Curious...the battery powered gravel cleaner...is that the type that filters the water into a bag, and then puts the water back into the tank? I think Eheim makes one that does that, and I do not understand. A regular hose-type non-battery gravel cleaner does the job, and does a water change at the same time, for a whole lot less money. On top of that, not ALL the fine crud is being removed if the water is just going back into the tank...just the bigger bits that get caught in the bag. And it's the really small stuff that needs to be removed the most.
Or am I missing something? (Never used a battery powered gravel cleaner, so I am unfamiliar with them...)