whare do I put my float valve?

[DJ88]

If your baffles are set up as you have drawn them steve you are flirting with a burnt out return pump. You want to maximize the water you have in that last area so that if water levels do fluctuate for any reason you don't run your return pump dry. For my mag 18 I am running an area that is 12x12x12. Even then I may run into trouble.

As well if you have your water level that low and you have a sand bed you are going to have a fast current running over the sand bed.

Say the baffles are 6 inches high and you try to put a 4" sandbed in there so it functions as a DSB. That leaves only 2" for water to flow over. And the shallower the depth the faster the water will move. As well it will create currents and will move the sand into your baffles then the pump. killing it. for example, I am looking at 6 inches minimum of water depth from the DSB to the waters surface. You want as slow a flow over the 'fuge as possible to maximize nutrient removal and filtration. as you have it now it will be a fast river flowing over your sand.

You may want to move the height of the baffles up to about 4-5 inches below the top of your sump. That is a general number. Mine are 6. that gives me about 15 extra gallons of H20 I can let flow from the tank to the sump if the power goes out.

Just my .02.