Like anything else you get what you pay for, and typically you need to spend about 600 to 800 dollars for a really good one. I have a $750 one from YSI that works well but I use mine for fish hauling to moniter oxygen while I'm hauling large quantites of fish.

You need to ask yourself if you really need one. What are you going to use it for? Typically for recreational ponders that have fish in low densities if you do everything right such as mixing the water column in summer with aeration there is no need to check D.O. If you have a problem and you have a D.O. meter what are you going to do? Usually once you have a fish kill there is nothing you can do and it's too late.

I don't even use mine under the ice anymore. If I keep snow off the ice when it gets over 1 inch and I am catching fish near the bottom there is no need to moniter oxygen. Additionally if you have green weeds and algae on the bottom you sill have sufficient oxygen.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.