I have 4 maxijet 1200s in my 40 breeder. 3 for current and flow and one for my Remora skimmer. Total of about 30x turnover. I think it is perfect. Zoanthids and other corals are growing quickly. The zoanthids tend to like the heavier flow areas, and my clove polyps and mushrooms tend to like the lower flow areas. I don't think I would want or need any more flow than this in this small of a tank. To answer the original question 20-30 times turnover should be good average to shoot for overall, and you zoanthids should be fine. Just be careful not to have too little flow or debris can build up between polyps and cause problems.