I haven't seen many posts on bottom drains for Koi ponds....just a few comments. In your opinions are bottom drains necessary for Koi ponds? How about ponds in general? The training that I have been to suggests that well designed ponds with bio filters with appropriately sized skimmers and pumps do not need bottom drains. Because of this training, I am not very familiar with bottom drains. Are they primarily for cleaning out the pond, draining the pond, or do they recirculate back to the filter? What is best practice in your opinion?