We have been in the throws of updating the feeding arrangements in the aquarium, including a new automatic feeder which we may well rely upon in the future. This would mean that all the food would be going in in one spot, and as some (most) of it falls straight into the gravel we think that this could cause a problem with decaying missed food.
So yours truly had a brainwave (I think it was actually waving goodbye!).
Put a small plate or something under the feeder. Well plates etc are round leaving quite a gap, so what is square - an old tile of course.
Not much of a blip, but it shows that it works. Just remains to clean the tank and put the tile down properly.