The first fish looks a bit unusual for a severum, may be the angle and it might be stressed or something though. Second is DEFINITELY a green severum.
The pleco, looks like a redspot which are frequently also called sailfins. But the fins don't normally have the much redder edging like that.
Supported only around the edges seems to be the norm in the US. And I've met many people who will violently argue with you claiming that it is the only safe way and that any tank will break if you support the whole base.
Discovered on the morning that the UPS would happily run a single filter, but not all 3. So I had to risk it and just run one.
And the nice little 5 hour "Often are for far less" outage according to the guy I had checking them turned out to be approx 8 hours judging from the amount clocks were off.
No deaths as of last report.
The motors don't care if they're moving air or water. It would be giving you around 12000ish RPM depending on voltage, so you'd just want to size the boat's prop for the current draw you're aiming for. Only concern would be cooling because it's air cooled not water cooled and you wouldn't get much air flow with boats being so slow.
Cooling would be a huge problem, and I don't know how mounting to a water prop would work...But powerwise you could go with a motor like this one for $140 US.
This one is rated at 8 horsepower and the motor itself weighs 200 grams less than your petrol motor. Of course, the 13cell lipo to power it is going to add a stack of weight.
I'm expecting about 3 hours out of a car battery running 3 cannisters. Maybe hoping is the correct term. Ideally I think you'd want to do something like just have an air pump running continuously on the UPS, no heater and any cannister or other filter run for like a minute or two every 10 minutes. Just enough refresh the water in the cannister.
Then she's not using enough. Just throwing the odd shell into the tank won't make any real difference. She needs to try something like bird grit which has a few hundred times the surface area.
It's only meant to be a one off. Why would I want to have 3 extension cords running to opposite ends of my house permanently.
And I'll have my father in law who is looking after the cats, birds and fish, unplug the UPS and plug everything back in where it belongs afterwards.