I'm afraid there is ...

I'm afraid there is insufficient information to be able to advise you.  What temperature is the cooling medium?  What metals are involved in the system?  What is the water quality involved supplying it. 

Having been involved with issues over the last 45 years the questions come first.  Somewhere between 10-15 % of closed loop systems have biological issues.  Some of these can be iron bacteria which are very difficult to grow on artificial media and take longer incubation times and only respond to very few biocides.

The first principle is to make sure that the system is pre-cleaned to remove suspended matter. If a system is new, it still needs to be cleaned to remove material present, which varies from oils or grease, corrosion products to bacteria to weld or solder.  Water flushing is not sufficient.

The choice of corrosion inhibitor will depend on the metals involved, the amount of water make-up, it will be restricted to ones approved in the food industry.  Certain systems may be limited in what they use, because there is a limit on the conductivity used in the water system because it will impact the process.

It really is a specialised area, that needs to be looked at professionally.