Ling time ago I had a version of this…. Not this exact model - was fully submersible and did a great job of cleaning algae off rock (make sure your running filter socks to get the algae as its scrubbed off).
I’m just getting back into the hobby and cannot find the exact scrubber I used to use, but this one is looks pretty close. I’m going to order one for when I need to spot clean. However, buyer beware, I havent used this exact product, just something very similar to it. Note: there are many versions of this available on Amazon - whatever you get must be fully submersible. Using something like this is infinitely better than a toothbrush.