Flow/current, via wavemakers, powerheads, pumps etc, serves many vital purposes.
1. Flow/current helps to keep live rock clean and clump free from settling detritus.
2. Aids in cleaning polyps that slough off by means of external cleaning.
3. It carries much needed food/nutrient to corals.
4. Often greatly enhances skirt length over time if on the medium to higher end.
5. Helps to remove waste and slim when new arrivals are stressed.
6. Moves uneaten food off the reef to allow other inverts on the substrate easier access as well as out of the tank via overflows.
7. Helps with surface water movement via oxygen/gas exchange.
8. It helps with calcification.
9. Causes a natural water sway/movement, back and forth motion which is extremely natural.
10. Current reduces shaded areas allowing more light penetration.
11. Causes a glitter line affect for Metal Halide users. Glitter lines are often viewed/seen in the ocean and it is a means of punching light deeper into ones system. The fluctuation from light to dark is a very natural one.
12. Prevents coral bleaching.
13. Current helps with evaporative cooling of the tank.
14. Prevents stagnation.
15. Removes film from the water surface, which increases light efficiency
This thread is not about turnover or means of achieving it, nor how said flow is achieved. It merely conveys the importance of having it and its short and long term benefits.