In general, I am not too thrilled about any goo inside the cooling system, there are probably a number of others that aren't either.
With this stuff in the cooling system it can clog smaller passages and holes, but a side effect could be, disallowing the right amount of coolant to flow, most likely in the radiator.
Plus, in my opinion this would only be a temporary solution!
If your coolant has the green stuff in it, then you have already something colored.

Is the indiated coolant temperature, back to nominal?

It is hard to find a leak that is hidden, thats for sure.
Perhaps, a local auto parts store has a pump that can be attached to the sytem. You may be able to rent it.
It can pressurize the system to it's nominal pressure and a bit beyond. Can be done while the engine is cold and is safer to investigate.
Also make sure, the radiator cap is the correct one!! It could be just steaming out...

If it loses pressure and you can't find it leaking out anywhere, there is only one other way to go!
Check your oil freqently for water contaminants.

If you can't find anything on the floor, the leak could also be somewhere in the really hot areas. Evaporating before it can hit anywhere. Perhaps, the heat exchanger itself has a small leak, or near the engine block a hose clamp etc.

__________________
Mostly, I don't know notin, I just know where to look.
I am looking back, to over 30 years in Electronics Design.
Electrons don't care if they move in a car, computer or relay!

95 W124 E320 M104.992 - Because, I love to repair, naaaah!
Over 221,000 Miles
Cheers,
Norbert