Water Gardening: Planning My First Pond... Any Advice?, 1 by SongsofJoy

SongsofJoy wrote:
A bottom drain is placed at the lowest point of the pond and is plumbed to a mechanical filter. When installed correctly, any debris on the bottom of the pond (fish poop, leaves, etc.) gets sucked down the drain and the solids are trapped in the mechanical filter, keeping your pond floor clean and healthy. The mechanical filter will need to be cleaned periodically. I clean mine once a month and it takes about 45 minutes to clean two filters. That is the only maintenance I do on my pond (apart from spring start-up and winter shut-down). I have an external pump which is the ideal for a system that includes a bottom drain. You can still add a bottom drain with a submersible pump, but most people who go that route plumb it to a skimmer, which works, but is more maintenance as the skimmer would need to be cleaned much more frequently.

One "disadvantage" to a bottom drain is that it is only effective if you do not put rocks on the bottom of your pond. This turns off many people who prefer a rock bottom pond. I was in that category once myself, but after a year of constantly battling water quality, I decided to give it a try. Rock bottom ponds only look nice if the rocks are kept clean, which can be a real challenge. Furthermore, rock bottoms also provide tons of nooks and crannies for mulm buildup (fish poop) which can create a toxic environment for fish. Even vacuuming won't get all the debris out of the nooks and crannies. So I emptied my pond, lugged out all the rocks, tore up the liner and started over. My biggest concern with removing the rocks was that I wanted my pond to look natural and I didn't want to see the liner. So I made all the sides have shelves that I lined with rocks so that the liner above the water wouldn't show. When I look in my pond, all I see are the fish, the reflection of sky and trees, and the plants. I don't notice the bare liner at all.

Many people get by without a bottom drain. In fact, it is very hard to find an article on pond building that actually suggests one, so most people don't even know about them. But for the impact they have, and the relatively low cost to add one, I would never be without one again. If you plan to keep koi, you should absolutely consider one because koi are a little more fussy about water quality than goldfish. But I would add a bottom drain even to a smaller pond that had no fish because I've seen firsthand the difference it makes in keeping the pond clean and clear.

The shed in this picture houses my pump and both mechanical filters. I was fortunate enough that the ground where the shed is drops off about 5 feet just behind the shed. We were able to build the shed over that drop-off and put the two barrels on a cement base underneath the shed. So the tops of the barrels are level with the floor of the shed so I can still use the "main floor" of the shed as storage.