Thanks for the link. That's a helpful tool. However, I'm already aware of how much sand it is. My question I perhaps should've clarified is am I gonna run into issues with a 3" sand bed if relatively fine sand in a 18" cube?
Run into issues? I wouldn't think so, no. If some spots get to deep, you will end up with a Deep Sand Bed Area, and can run into Hydrogen Sulphide Bubbles. But if you get a good CUC that aerates sand, I wouldn't see you having any problems.
Were you planning on cleaning the sand bed on a regular basis or just letting it go? Three inches of sand is kind of right in the middle of a SSB & DSB. These are usually maintained differently.
Was hoping to just let it be and let a combination of a decent sand crew do it all. But I'm also prepared get more hands on in terms of the sand bed. Hearing a lot of mixed opinions and experience with the whole "middle ground" on ssb and dsb. Which is why I wanted the forums 2cents.