Rez heaters and light?

Might be a noob question, appologies,

I have a 4 pot tank oxy pot, soon to start.
Where I live (getting cold)and with heating costs I figures I'll need a water heater rather than a water chiller, as I'll be using a 300w LED and an extractor fan in a tent, 1mx1mx1.8m.

Its a submerged fish tank type heater, 150w with a thermostat set to 18c, its lowest setting, so it won't turn on unless the res temp drops below 18c, and will just maintain 18c before switching off again.

The only thing is it has an orange LED power light in the glass tube... I've been doing some refinements on the air pump tubes (clear) by wrapping them in black duct tape where they enter the rez. Should I be worried about this power LED?

I could wrap duct tape around that bit of the heater? but would the glue from the duct tape mess with the chemical balance of the rez?

This is the style of heater I have:

Thanks for any advice/input

I've used heaters like that in the past and never noticed any issues.

Thank you,