Keep the current drain. Run a return line up and over the top with 3/4 inch tube and a something like this:
https://www.marinedepot.com/U_Tube_...MIrJTUhJuw4gIVWLbACh1fggGiEAYYASABEgJX3_D_BwE
Run another intake up over the top to another pump for a closed loop with the three returns. Get a stronger pump for this. Closed loops are awesome for flow and stuff.
None of those pumps need 3/4 inch. Once you lower the diameter, the head increases, but so does the power - output depends on the model and head height. We were able to get about 600 GPH up 20 feet with a Mag 12 with 1/2 line... at about 100+ watts (ouch). Mag 7 is a great pump for 1/2 inch and is 400-500 GPH at 4-5 feet of head. Ehiem are nearly all 1/2 too. You can move nearly any AC pump to a smaller neck size.
https://www.marinedepot.com/U_Tube_...MIrJTUhJuw4gIVWLbACh1fggGiEAYYASABEgJX3_D_BwE
Run another intake up over the top to another pump for a closed loop with the three returns. Get a stronger pump for this. Closed loops are awesome for flow and stuff.
None of those pumps need 3/4 inch. Once you lower the diameter, the head increases, but so does the power - output depends on the model and head height. We were able to get about 600 GPH up 20 feet with a Mag 12 with 1/2 line... at about 100+ watts (ouch). Mag 7 is a great pump for 1/2 inch and is 400-500 GPH at 4-5 feet of head. Ehiem are nearly all 1/2 too. You can move nearly any AC pump to a smaller neck size.