Bottom drains in a Koi pond are highly recommended and you will probably hear Koi Keepers advocating for every pond to have at least one, if not more! So what is the big fuss? Let's talk about why they are considered a must...

Bottom drains are installed on the bottom of the pond and are typically 3" to 4" in size. Some are bigger - I've heard one person had 6" bottom drains. They are typically plumbed out prior to liner and do require that they are placed so all debris is drawn to it; otherwise, the waste can sit in corners and never get cleaned out of the pond.

The bottom drains are attached to the liner and must be waterproofed to ensure that they do not leak. (The newer bottom drains make this pretty easy, but it can make folks nervous to cut a hole in the liner!) These bottom drains also require that the pond be shaped to ensure that all the waste is drawn to the drain for cleanup. 

The reason that they are so highly recommended is that fish waste does not get picked up by skimmers and submerged pumps can get overwhelmed by the volume of waste generated by Koi - especially during high growth season. Koi can be fed quite frequently (up to 10 times a day) and that can result in lots of waste. Bottom drains do a great job of getting this waste out of the pond and into the filter. 

The alternative to a bottom drain is a pond vacuum or substrate. Most folks with substrate (rocks/sand that is meant to house bacteria that eats the waste) find that it needs to be cleaned quite frequently and depending on the waste may not provide the desired benefit. Additionally, the substrate can present a great home for other bacterias that harm your Koi and treating a pond for harmful bacteria can be expensive and hard on your Koi. 

There are lots of benefits to having bottom drains - I've just touched on a few of them. I personally have 2 bottom drains that are 3" in size for my 3,000 gallon pond. 

I'm interested in hearing your opinions and learning from your experience!