Your HippoTile can be power washed to look brand new.
Hoses, leaf blowers and vacuum cleaners have also been used effectively.
Very occasionally, one or two HippoTiles may become less secure than the others around them.
This is remedied very simply.
Cut some thin pieces off the short end of a HippoTile offcut. The pieces should vary between 5mm and 10mm thick.
Pick up the ends of the two apparently loose HippoTiles. Sandwich one of the slivers between them. And press back down. Tap with sledgehammer to secure.