Mineral Mud is a waste of money in my opinion. Here is a micro-image of the stuff that was called Miracle Mud by the company that started the idea years ago. It's mostly silica sand with some organic material mixed in. Some good clean dirt from your back yard could do just as well. Hey, in fact I've done that before. As far as I could tell, it didn't make much difference.

Utah or other Oolitic Sand at the bottom of the Refugium at 1-4" deep with Chaetomorpha growing in the water above is the best use of that area, providing more biofiltration than any other method. As long as water flows through the Chaeto, there is no need for it to tumble. Keep the Chaeto harvested regularly and if Caulerpa is wanted, place it upstream from the Chaeto, otherwise Caulerpa will not get enough to eat and will eventually die off.

As far as the Return Pump area, the pump needs to be placed in a position relative to the water level such that if the drain clogged for some reason the pump would not push enough water up that the display overflows. If automatic top-off is not used, find the level at which during a power outage, the draining water will not overflow the sump. We often use a marker to mark the running level and maximum level. 

The positioning of return nozzles is crucial to avoiding a siphon down the return line which would overflow the sump. I recommend setting the top edge of the return nozzles just at the water surface so the water cannot siphon back down much before the siphon breaks. 

Aloha,

Mark  

 

If you really dont like it being adjustable you can take a peice of plastic egg crate (cut to desired hieght) and slide it under the lip of the plastic divider.