Heating Large systems

I am setting up a 150 gallon stock pond but it’s going to be a part of an overflow rack system. In total it should be around 350-400 gallons depending on how many tanks I decide to set up in the future.

I should add I like to run my tanks around 83-87F. Especially for discus.

How would someone heat something like that? I was thinking just running 2 or 3 Eheim Jager 300W but I wasn’t sure if this was the best solution.

Any heater recommendations?

My basement can get pretty cold here. I could probably insulate it in some way. If anyone has a budget orientated option I would love to here