Just dumping the water from your filtration system back into your pond is a waste.  A useful Koi pond build tip would be to use that water to aerate and get a current flowing throughout the pond. Your Koi might not thank you for this but it will aid in supporting their good health and quality of life.

There’s nothing fun or exciting about a ragged piece of pipe sticking out into your pond and pumping water back into it.  It’s an eyesore, it is potentially dangerous to your fish, and it’s just uninspiring.

Why not imbed that pipe into your pond’s wall at an angle and cut it flush?  Now you’ve got a directional flow.  Have more than one return?  Work out the design of your Koi pond build so that all of your return pipes push the water in the same direction.  This creates a current and gives your Koi something to swim against.  It’s like exercise . . . well it is exercise and will help your Koi grow to be big, healthy, and strong.  Just be careful not to create too strong a current or your Koi will not be happy.

Water returns work best if they are neither too deep nor too shallow.  Shallow returns will disturb the surface of the water whereas deep returns will stir up sediment along the bottom.  About 300-600mm below the surface is an ideal Koi pond build design.  Deep returns can be installed but mind that you don’t direct the water flow right at a bottom drain.  That’s just pointless as the water coming out of your return has just been filtered.

Take care to place your returns well and they can:

1)     Prevent dead spots within your pond. 

2)     Help filter the water by directing the flow toward the skimmer and/or settlement chamber. 

3)     Help keep sediment and solid waste from building up in a certain area by directing a jet that way.

Another option is to add a venturi

What’s a venturi?  It’s a nifty little device that adds air into the incoming water.  Koi pond build designs can never incorporate having too much air circulating in the water.  It’s essentially a piece of pipe that’s open to the air on one end yet attached to your water return (a few inches from the point where it enters your pond) at the other. 

How does it work?  The kinetic force of the water flowing past the point where the two pipes join pulls air into the water return pipe, mixing it with the water.  That oxygenated water is that spat out into your Koi pond.

Venturis are a fun way to add oxygen to your water but keep in mind they can be noisy and create bubbles which can make your Koi hard to see.  Though within a Koi pond build design you can effectively silence a venture with some insulating foam, it’s best to locate them out of sight; however, the location of your water return is a fixed variable and that may not always be possible.

Having a dedicated air pump may be a better option.  It will protect your Koi pond from stagnation.  How?  If your main circulation pump ever fails, your pond will still be oxygenated.  A dedicated pump also means you can locate the air outflow (whether it’s an actual air bar or just a piece of tubing with holes drilled into it) out of sight around a corner or behind an architectural element.

A definite with any Koi pond build design is to never introduce compressed air into your pond.  If your fish breath this, tiny bubbles will form in their capillaries and can block blood flow to the tips of fins, causing fin rot.