40 gallon water box

[Bcook1016]

For this tank it’s more or less a cube, for 40 gallons does this need a sump and how big 20 gallon? Should I use small rocks at the bottom instead of sand? Is it better for maintaining

 

[Mr. Mojo Rising]

no tank "needs" a sump, its just nice to have so you can hide all the equipment inside. Without a sump, you use hob equipment which works just fine, but can be unsightly to see all the equipment. But if you wanted a sump, a 20 gallon would work well - I use a 20 gallon sump on my 40 gallon tank (but I have 3 other tanks that have no sump)

You mean small rocks in the display tank instead of sand? Thats a bad idea, all the food and crud and stuff will slip between the rocks where the clean up crew cannot reach it, it will rot and create nutrient issue's and algae issue's.

But is that an AIO tank?