This product is ok, in my opinion, for a pond where you are generally already on top of the problem lurking at the bottom of the pond. If you are trying to rectify a considerable period of neglect and you have a lot of silt at the bottom, then you may be best getting one of the pond vacuum pumps. For getting up larger items of debris, such as leaves, this doesn't do too bad - the venturi effect sucks the leaves up into the bag and traps them. It will pick up silt, but it can't trap it, so it just recirculates the silt and before long you can't see a thing. I guess this isn't too bad if you have some seriously good filtration for your pond, that can be back-washed to clean the filters once you have got all the silt up into suspension and your pump has presented it to the filtration system.
For the price it's excellent and well worth tryng first to see if it tackles the problem. If it doesn't, then you haven't wasted your money. You would then just have to invest in a vacuum pump and use the cheaper venturi device when you get some leaf build-up. Better though to avoid allowing the surface debris to sink to the bottom in the first place - get an OASE Swim-Skim, which works surprisingly well.
So far as getting your water clean for ever more - dream on! Cloudy/green water is due to billions of algae cells whose numbers explode once the water temperature and light levels start to increase. True, it's more likely to occur if the algae can feed off lots of nutrients due to decomposition of gunk at the bottom of the pond, but even so, you're unlikley to get on top of the problem with this device and filtration/UV alone. It's all about balance and this device can certainly help, but this won't be the thing that gets your water crystal clear. Get some flocculants and maybe algicide/blanket weed killer also.
In summary, when the pond level gets a little bit low due to inevitable evaporation, etc., rather than just putting the hose in, I'll put this device on the end of the hose and run it along the bottom periodically. That way, I'll probably keep on top of the problem now that I've given the pond a good clean with the OASE Pondovac I bought shortly after purchasing this venturi device.