Have a friend who is planning a new set up he wants to do miracle mud and add a uv his question is would having the uv defeat the purpose of using the miracle mud this would be a fish only systeM
No
Miracle mud gives a slow release of trace elements, and gives you a low oxygen/anaerobic area which can be accomplished in much less depth than with a deep sand bed which will consume nitrates.
A uv has nothing to do with either of those benefits that someone would expect by using miracle mud.
FWIW have found Caribsea, and Fiji mud just as good.