@RatioTile There was a sign I believe, but I didn't take a picture of it. I thought I remembered that it said plaice, but with no pic I couldn't be sure. It didn't say what species it was, but it most resembles the scale-eye plaice, as it had faint orange spots and distinct corners on the fins around the edge. However, there are no records of that species on JAZA.
@RatioTile When I was there they were all extremely active, even the ones on the bottom weren't buried and moving around a lot. Very unusual for flatfish, but was great for photos.
Could also have been the European Plaice (Pleuronectes platessa), which also has the faint orange spots. IIRC the tank was the North Sea tank, which makes sense for the European Plaice, they are found there.