I tried that.....once, and it’s not that great for pond debris. Problem is that it fits a 5 gallon bucket, which will fill up very quickly. Then, you spend the majority of your time emptying the thing, setting it back up, etc. But the only way to know if it will work in your situation is to try it.
I actually use a Sears wet/dry to clean the bottom of my pond. It has an discharge button which I use to discharge the water with a hose. After a few times I have to open up the vacuum and pour out the debris which has been sucked up from the bottom of the pond.
I think way back when, there was a post by one of the guys who did a DIY bottom vacuum using PVC pipes and some kind of container.
I tried our wet-dry vac and found it to be slow going. Lots of stopping and dumping and re-starting.To me a net is a far better device - fast, simple, easy to store, and anyone can use it.
We went through a bunch of "pond" nets (sold by pond stores specific for ponds) in the beginning and were disappointed in the quality and longevity. They fell apart after several months of use.We finally switched to a pool net - a bit more expensive, but far more durable and the one we bought came with two interchangeable heads. One is flat and wide for bottom scooping and one is smaller for getting into tighter spaces. We store ours outside year round and the net has not degraded one bit in five years.
You won't get the fine debris with a net, but I'm not all that concerned about the fine stuff. And if you keep the leaves scooped, you'll get less fine debris build up as well. I would recommend a net over any kind of vacuum set up any day.
Anytime your fish don't eat the food you feed them, you should stop feeding. And only feed what they will eat in a few minutes time. Fish that are used to being fed should respond with enthusiasm when you approach the pond. If they ignore you, they are telling you that they don't need food. You never want food left in the pond - better they should be a little hungry than to foul the water will old food.
You don't have to feed your fish everyday. If you just have goldfish and no koi you don't have to feed them at all. They will eat bugs, worms, flies, algae, anything that falls into the pond. I did not feed mine for several years and they did just fine.