Hob overflow with lift pump. Into whatever sump you want
I recently found a couple of those old Aqua Lifter pumps in my stuff from a while back lol! OP, If you decide you need one of these pumps, shoot me a message.
No, under, the sump would just be tall instead of long
I think a pic of your tank and space for your sump would go a long way here ;-) I don't doubt what you're saying, but in my mind I'm not sure how you have a 150 gallon tank, and can't fit even but a 20L or 40B under it (or next to it)?
I have never used one of the no-drill HOB overflows because some of them were definitely prone to failure, and I wouldn't want to see your 150 end up on the floor. But, there are members here at R2R who swear by the HOB overflows where you do not have to drill your tank. I think maybe Eshoppes makes one of the more trusted of these overflows? I'm sure someone will be by shortly to let us all know that they have been running their tank for years with one of these overflows.
Perhaps, you could try one of those HOB overflows and mitigate potential disaster with some well placed flood alarms, or some other well thought out monitoring system?
As for your vertical sump design, in my mind I'm seeing more of a trickle filter tower or wet/dry style of filter. These were really popular back in the day, but fell out of fashion as they can get dirty and become a "nitrate factory". But, I think with some planning and care, you could definitely make a sump work that is more or less a vertical tower.
My last thought is that I personally hate canister filters, in freshwater tanks as well. I just think they are such a pain in the you know what to clean, so I typically don't clean them enough. And, I've had canister filters leak in the decades now that I've been fishkeeping.
Would you consider trying two or three large Fluval/AquaClear 110 Hang On Back filters? I guess I don't know what you're keeping in your 150, but these filters can move a lot of water, and you can likely transfer over some to all of the media in your canister now. These filters have a pretty good following here, with lots of mods you can make to tweak them to your system. I've never, ever had one leak on the floor, and you definitely don't have to drill your tank to use them
Personally, I think these Fluval/AquaClear HOB filters are the best hang on backs you can get, and that includes the otherwise popular SeaChem Tidal HOB's, in my opinion.
There's other HOB gear too, from 'fuges to algae scrubbers. Maybe some combination of HOB gear would work for you?
Best of luck with whatever you do!
