The only difference
rtween the Eheim and rthe Hagen is the Hagen is made to work directly on a Aqua clear HOB filter, and includes an adapter to fit the 1" water inlet tubes on the Aqua clear HOB, or the smaller 1/2 or 5/8" diam inlet tubes on the Ac20 mini filter. The Eheim unit does not contain the adapter and is geared mainly for one size. Thats the only difference between the two. I really do not know the exact size of the tube but its whatever the Aq and Eheims are and best thhat I can tell are like 1" and 1/2 or 5/8" tubes. No mods are needed to make it work as long as it will fit your pickup tube. That is not a real problem anyhow with a bit of ingenuity they can be adapted. IMHO they are a much valued add on to any sized tank as they do a super job of keeping surface film removed, and frankly for the cost, there is not too much that one can buy for a aquarium in that price range that acutsally does work and works quite well. I wold recomend adding the two orings or a wrap of sa heavy duty rubber band around the clear plastic floating portion though to restrict how far it can drop down into the black portion. A drop of 1/2" or so is more than sufficient, so when the tank is fully topped off, and float portion is floating, place rubber band or orings on float portion 1/4" or so above the black piece. Stick to sides of glass with suction cups and is only other install. Its straight forward and works well like I stated previously. I have substituted ridgid plastic tube inplace of the flex tube and have used 5/8" diam pond tube which is black and not corrugated, and have the skimmer located in the opposite corners in some of the aquariums, so yu can easily extend that flexible piece of black tube to relocate the inlet tube anywhere you desire.
Flow is adjusted between the upper portion and the lower portion so the upper remains sucked slightly down so water inflows between the teeth. The plastic rod that extends upwards out the center of the clear piece is turned to adjust the flow, so any additional adjustments can be made without having toget your hand in the tank.
