Thanks how much Rock and sand is needed in the sump
I myself would use a DSB in the fuge, but looking at the way your wet/dry looks, I would be afraid of the sand since it might get into the pump, so I might just fill it up with small/med size rock or rumble or you try to add a piece of acrylic baffle so the sand doesn't get into your pump chamber.
How do I prevent the bubbles?? I need something to stop the water coming into the sump to stop creating bubbles
Using a filter sock would help, bubbles to the fuge part wouldn't be a problem as long as it doesn't pump up micro bubbles into the display, or place an piece of acrylic as an over baffle before the under baffle would stop the bubbles going to pump chamber.
Also should I keep the light on while I'm cycling in the sump
Take the sand out of there. Or at least put it in mesh bags.
I have a hose that will work. You can have it.
Put the hose into a filter sock, or put a pitcher or small bucket in sump with hose into it so bubbles float to top.
You need a skimmer and room for it.
Samster brings up a good point. You need to have a small hole at top of return line, just below tank's waterline that acts as a siphon break in case the pump craps out or power fails. Then you must keep water level in sump low enough so that when power goes out the amount of water that goes down into sump before the siphon is broken isn't more than the sump can hold. Otherwise, flood
Ok understood, would a HOB skimmer be better to put in back of the overflow?
What would happen
You could put a HOB on the fuge part of the wet/dry, but I don't think there are HOB's that's adequate enough for a filled 75 gallon tank.
Without a siphon break, the drain will vacuum out all the water in your overflow until it is broken by air, the wet/dry if doesn't have enough space for back siphon or enough capacity for the water in display will cause a flood, and the sand getting into pump will cause damage to pump.
Understood so how would I get this away without stopping the whole system again
Need to stop pump to see water level in sump, and mark your max water line.