I do have snails but if you look at natural ponds (in fields) – you will notice that they are all crystal clear unless the local angling clubs have been there. Angling clubs appear to destroy natural ponds. None of the natural ponds that I have seen have filters and electric UV systems.
As far as I can tell, a pond simply needs a good combination of the right type of plants. Ones at the bottom and ones that have floating leaves. Also, make sure you have plenty of creatures in the water. Having said that, I didn't actually import any creatures and I didn't have any border controls – they are all immigrants and simply arrived all on their own. Frogs, newts, dragon flies, snails, beetles, water boatmen – weird spider things and pond skaters.
Save energy and go natural. Burn the energy on your lathe and miller.
Phil H