You are asking if there is a better way to heat the ambient air?

The best answer I have is to use a different enclosure. Plastic tubs really can only easily be heated with a UTH they don't make major changes to air temps. Depending on how much higher your power bill is it may or may not be reasonably priced. I would look at something along the lines of a vision, AP, or neodeshia. They can be regulated with a UTH and fluorescent lighting maybe installed, they are cheap to run and pass off enough heat to significantly alter ambient air temps. (IE my room today is 66ºF and the enclosure running FL lights is 83ºF) I run deep blue LED over night. The electronics also run in the 100º range and that too will help ambients. The enclosure itself is more efficient at holding heat in. If your power bill is even 50$ more a month it might well pay for itself in less than a year.