Almost there, but...

[Aquattro]

3/4" is on th esmall side, so the MAG 7 might be the max you can use for a return. I use a MAG 7 to return to my frag tank (40g) and I feel it isn't anywhere near enough. Ideally I would want a MAG 12 on a 90g, but the 3/4" output won't handle it. As long as you provide enough current inside the tank by other means, you should be fine.