Aqua Gadget 15 Gallon Hydrofill.... Float level acid safe???

[JTP424]

Ok...
So I picked up one of these used:
ATO Aqua Gadget
It's caked with algae....
If I dump in diluted muriatic (no easy way to clean inside the water level....)
Will the acid eat the little red pellet?

 

[lapin]

Will the acid eat the little red pellet?
What is a little red pellet? picture?

 

[JTP424]

In the bottom of the reservoir is this little floaty....

 

[lapin]

I would assume the floating pellet is plastic based. Mild acid should have little effect. If its glass then mild acid could dull the finish.