Powerhead mod

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Active member
Dec 12, 2004
Hi .....crazy post but iI thought it was interesting.

I had a berlin red sea skimmer given to me a few weeks ago to run on a tank I have....only problem .....I had no decent pumps to operate the venturi on the skimmer.
Well the obvious solution would be to go out and buy the correct said pump!
But....I thought what if I try an Aquaclear 802 powerhead I had lying around (one of 4 spare!)
The results were not very good as I anticipated.
I wondered what the problem was....the most obvious was the lack of pressure from the 802....2nd problem the flow rate was also to low.
Well seeing as I had so many 802's hanging around I felt in a bit of a DIY messing about mood!...am sure you have had a few yourselves!

First thing was to study the powerhead.....the impeller seemed to have loads of room for rotation with what seemed like miles to much distance between the impeller and its housing.

Now as the impeller blades rotated they forced water through the outlet as impellers do, but I thought what if I could alter the size of the impeller vanes and at the same time reduce the 'Gap' between the tip of the impeller blades and the outlet inside the impeller housing......thus forcing the water out without it being able to flow around the tips of the impeller vanes.

So I got myself a tube of superglue......an old clear cd......and a pair of scissors along with some sandpaper.

I carefully measured the new impeller vanes to creat as tight a fit inside the housing as I dare without impacting on the walls of the housing.

The Modification took just over an hour and the results were amazing to say the least!

A standard AQuaclear 802 is rated at a modest 1514 ltrs /hour or 25 ltrs/ min =5.55 gals/min

My first test was to see how much my 10 gal bucket filed up in a minute with a standard 802 (water level in tank was the same level as the bootom of the bucket to reduce gravity syphon effcting the tests).

In one minute the water in my 10 gallon bucket was at approx 4.8gals (estimated the gap between 4 and 5 gal marks) = 288 gals/hour = 1307 ltrs/hour!....this was a bit surprising and down from the manufacturers given specs.

Now after my modifications the same test gave 8.2 gals in a min!
This relates to 492 gals/ hour! or 2233 ltrs/hr.

2233 divided by 1307 x 100 = 170% better!! ( I hope these sums are right! if not please put me out of my misery!)....

Not a bad increase for a cheap tube of superglue and an old clear cd!

Well its been running the skimmer well over three weeks now and the results are very good.........the extra water pressure created with this simple mod is quite amazing and although I never measured the head hieght with a hosepipe in the garden the powerful jet of water in the bucket was so obvious....it really was a huge difference!

Now Am not suggesting anyone goes out and totally knackers their prized power heads but it does make you wonder what testing they do with some poewerheads in the factory were they are made.

I wonder why there are no alternative enhanced commercial impellers for such powerheads...would be cheaper than a new powerhead upgrade.....

Anyway heres a few pics to show the results.....

I did say it was a daft post but what the hell......I love some of the posts on the DIY section.....mojoreef's skimmer and Dons skimmer and venturi etc are great!....and just show what can be acheived wit ha little knowledge and a steady hand!
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Feb 13, 2004
Spokane, WA
Very cool- Nice job on the cut & fit- I would bet it was tedious.

It would be nice to know what the power draw was before/after too.

Thanks for sharing!



Import Fish
Jul 30, 2004
Ettrick, VA
That is a great idea, wonder if this would work with RIOs?

I also wonder if the motor has to work harder to turn the impellars? Could this shorten the lifespan of the powerhead?


Active member
Dec 12, 2004
I dont think it could shorten the life of a powerhead they are just electro magnets sealed in resin....the extra resistance generated by the increased vane size on the impeller would am sure cause a greater power usage on the powerhead resulting in increased power usage and temperature increase aswell. ( all pumps and power heads produce heat as a result of friction and electro mechanical aspects of their designs).

As in any motor the coil design would limit the available wattage, its just a matter of how much slack there is in the system....

Ultimately you would reach a point were if you kept on inceasing the vane size of the impeller the rated coil of the powerhead/pump would be unable to cope with the demand and effieciency would start to decrease....its a simple curve up....peak at the top then curve down again...at a certain point at the top of the peak there would be insuficiant power available from the coils of the elctromagnet to satisfy the bigger and bigger vanes......effieciency would thus decrease along with pressure and water flow......of course its impossible to follow this curve all the way on its downward side of the peak due to the impeller housing restrictions limiting ultimate vane size.

The secret is determining were the top of the curve is in every pump.....some pumps may have a large margin of error thus allowing considerable gains to be made......whilst others may be at their peak of their rated designs.

If you want to try this mod....most important is the clearence top and sides of the impeller housing...dont try going to big on the vanes or they may snap due to the torque torsional forces exceeding the material strengths.

I would have a guess and say that most pumps have an inbuilt margin of error to reduce failures of the impellers etc.

Zephrant ''It would be nice to know what the power draw was before/after too''...i agree i only wish i could test the increase on the draw....

i wonder if it aproximates with the % gain on the pump output? or maybe it could be less than you think....after all a lot of the energy imparted to the spinning impeller blades before modification was wasted as the water was being forced over and around them as oppossed to being forced through the outlet pipe!

with a smaller gap now nearly ALL the water is forced through the outlet making for a much more effiecient setup.....therefore the powerhead is more effiecient so power consumption increase might be negligble!

Its great to mess with stuff like this.....the propellers fitted to aeroplanes can be modified to gain extra power just by altering their angle to the air...or adding an extra propeller blade....am sure powerheads can be tweaked using similar principles of extra blades/bigger blades etc......even changing their shape...ie fatter at the end or some other mod would make a difference.....
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