I replaced my flexible hose from my return pump to the hosetail on my hard plumbing return pipe yesterday, The reason being the black corrugated flexi hose has a habit of going hard and splitting on bends. I bought a much better and more flexible hose used to plumb washing machine and dishwasher wastes in. I cut it to length and one the ends were heated in some very hot water I managed to force it over both hosetails. I feel a lot safer now and the bend in the pipe is much smoother. You could use this hose on external reactors in tight places and it even comes with a bend holder which would go over the edge of a sump for instance.