I would choose the RO 152 over the AquaMaxx - just don't think the AM is large enough for 100g of heavy bioload. The other option under $300 that comes to mind is the Bubble Magus Curve 7 - their depth recommendations are too deep, and would work well around 7" IMO. I am sure there are a couple of others that would work, but under $300 limits the choices...