Thank you for your clarification, Matthias!

I was aware of the fact that the fish protection function is embedded in the pump (or at least Tunze says so), but I was wondering if the controller wouldn't be able to disable it. I mean, the pump proper (the part in the water) needs to receive some intermitent electric potential at its input in order to be able to execute the expected spins. It would have been possible that an inadequate control potential (from the controller) during idle time to make the intermitent pump potential (from the pump power supply) fall under the necessary value.

I understand from your reply this is deffinately NOT the case. Please correct me if my understanding is erroneous!

...And if I'm right, this discussion has to be continued in Tunze's yard (which is quite difficult, as they clearly forbid controlling their pumps by any other device but their dedicated controllers).

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Many thanks to all contributors to this thread!