Is underfloor heating possible with a "pool" heat pump?

Hello, I am currently in the process of converting a basement room into an "aquarium cellar." Since I want to avoid high running costs, I will insulate the room well to be able to heat as efficiently as possible. However, completely avoiding heating is not possible in any case. Therefore, I thought I might try it with underfloor heating in combination with an air heat pump. With my required heating load of <2500kwh and my acquisition budget, I came across pool heat pumps, which may not be quite as efficient as "real" ones but would still keep the power consumption lower than, for example, an instantaneous water heater. For me, the air would be drawn from an adjacent room, which naturally (due to its location underground and its adjacency to the aquarium cellar) in extreme cases might get as cold as 5 degrees, which in my opinion would make the operation even more attractive. However, unfortunately, I am an absolute layman in this field, and my self-studied knowledge has unfortunately not revealed the one problem that would cause it to fail, although I have often read that people rather advise against such a construction. Another important piece of information is the temperature of 26-28 degrees that the room should reach.

If you transfer heat from a closed room with a temperature difference of over 20° Kelvin into another room, what do you think happens in the first room?

- Performance of the heat pump
- How is the efficiency at low temperatures (pool pumps are not designed for this, antifreeze may be necessary)
- Own circulation pump needed. Pool heat pumps are designed for 4 cbm per hour and more, the normal heat pump runs at 0.6-1 cbm.
- Air supply must absolutely come from outside!!! Alternatively, place the device outside.
- Have a good amount of money in the account to pay for the electricity consumption? Pool heat pumps are designed for clearly positive temperatures, at subzero temperatures they may not be operational at all. And the pump that delivers 4,000 liters per hour also consumes a lot of electricity (independent of the fact that you need proper piping to move that volume of water at all) – it will probably require 4-6 kWh of electricity. Per day!!! Besides the electricity for the heat pump.
- Pool heat pumps have no great control or heating curve
- I don’t feel like listing more reasons why this idea is no good...

Ok good, I see that the idea is rubbish... It would have been too good to be true anyway, but I could have figured out some things myself. Are there alternative heat pumps that would be suitable for the whole thing and maybe not cost a fortune? Or is it perhaps more sensible to work with a tankless water heater or something similar?