Lily Pipe Setup and Positioning for Planted Tanks
A lily pipe goes in four steps: soften the hose, mount the inflow and outflow on the same wall, set the depth, and place your CO2 diffuser so bubbles do not get pulled straight into the outflow current. Get those four right and water moves in a smooth loop around the tank.
This guide walks through each step in order. It also covers what changes when you install a PETG lily pipe instead of glass. Our lily pipe sets use a 16/22mm barb, the same size covered in our hose size guide.
Softening tubing before you connect it to glass or PETG
Cold hose is stiff. Warm it first and it slides on with far less force and far less risk of a cracked pipe.
Dip the end of the hose in hot tap water for about a minute, or run hot water through it. It goes soft and a little stretchy. Push it onto the lily pipe barb with a gentle twisting motion, not a straight shove. Let it sit for a minute once it is on. The hose tightens back up as it cools, which is what gives you the seal.
| Set | Hose fitting | Pieces | Colors |
|---|---|---|---|
| Inflow (draws water in) | 16/22mm | 4 | Black, white, Frost |
| Outflow (returns water) | 16/22mm | 4 | Black, white, Frost |
Hose fitting size comes from fitment-data.ts, sourced from Eheim and JBL's own spec pages and confirmed independently by both manufacturers. Piece count and color options come from our product catalog.
Same-side mounting for circular tank flow
Mount the inflow and outflow on the same wall of the tank, a few inches apart. This sends water out, around the tank in a loop, and back to the inflow, instead of straight across in a short path.
Mounting them on opposite walls can short circuit the loop. Water travels the short distance from the outflow to the nearby inflow and skips the far end of the tank, so plants and substrate on that side see less movement.
Same-side mounting also keeps both hoses running to the same corner, which makes for a cleaner look behind the tank and a shorter run back to the filter.
How deep to set the inflow and outflow
Set the outflow tip just under the surface, deep enough that it does not spit air and shallow enough that it still ripples the top of the water. That surface movement is what brings in oxygen.
Set the inflow lower in the water column, clear of the substrate and clear of any plants that could get pulled against the slots. Leave a few inches of open water around it so nothing blocks the pull into the intake.
Protecting fragile glass during install (and why PETG does not have this problem)
Glass chips or cracks if it takes a side load while you push a hose on, or if it knocks against the rim of the tank during install. Go slow, support the pipe near the bend you are working on, and never force a fitting that will not move. Wrapping a towel around the pipe while you work is a cheap way to catch a slip before it turns into a chip.
PETG does not have this failure mode. It is a strong plastic, not glass, so it will not shatter if it gets bumped during install or bumped later by a net or a piece of hardscape. That does not mean it cannot be damaged at all, just that a knock will not turn it into sharp pieces in your tank.
CO2 diffuser placement relative to your outflow
Keep your CO2 diffuser away from a spot where its bubbles get pulled straight into the outflow current and swept to the surface before they can dissolve. A common setup places the diffuser on the opposite side of the tank from the outflow, or low and off to the side of it.
The goal is more contact time between the bubbles and the water, not less. Watch where your bubbles travel after a water change and move the diffuser if they are escaping fast instead of drifting and shrinking as they rise.
Frequently asked questions
Do I need to warm the hose before installing a lily pipe?+
It helps a lot. Cold hose is stiff and harder to push onto the barb without forcing it. A minute in hot water makes it soft enough to slide on with a gentle twist.
What size hose do TankRig lily pipes use?+
Both our inflow and outflow sets use a 16/22mm barb, the same size as an Eheim Classic 600 intake. Check our hose size guide if you are not sure what you have.
How deep should I set my lily pipe outflow?+
Just under the surface, deep enough that it does not spit air but shallow enough to still ripple the top of the water. That surface movement helps bring in oxygen.
Will a PETG lily pipe crack like glass?+
No. PETG is a strong plastic and will not shatter the way glass can if it gets bumped. We print in PETG, the material aquarium keepers have used submerged for years. Rinse it in clean water before it goes in your tank.
Where should I put my CO2 diffuser?+
Keep it away from the direct pull of your outflow current, or the bubbles get swept to the surface too fast to dissolve. Opposite the outflow, or low and off to the side, is a common starting point.
Can I mix a black inflow with a Frost outflow?+
Yes. Inflow and outflow are sold as separate pieces, so you can match colors or mix them, whatever looks right in your tank.
A note on safety
We print every part in PETG. It is the material aquarium keepers have used submerged for years. We cannot promise how any part performs in your tank. You know your tank and your animals best, so the call is always yours. Rinse each part in clean water before you add it to your tank.
Our lily pipes are still being fit-tested
We are not selling our lily pipe sets yet. We test every size before it ships, so it fits right the first time. Shop our adapters while you wait, or check back soon.
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