100gph to 200gph by inexpensive mod

You can greatly increase the filter rate of the standard Fluval Edge filter (equivalent to an Aquaclear 20) by changing the existing impeller to the impeller used in the AquaClear 50 (impeller number 634). This is not a guess or speculation, I ordered the impeller replaced it and had a dramatic increase in flow.

Before there is a big debate whether it is exactly double the flow, I am a Chemical Engineer and realize that there are many factors that would possibly prevent the flow from being exactly double. The most important is that the filter media cross-section that the water is being shoved through is about half of the AquaClear 50, and this will cause a greater pressure drop across the filter bed. Nonetheless, the flow is greatly increased through the filter. In fact, the lowest setting with the new impeller is about what the highest setting was with the old impeller.

(Note: An easy way to find the impeller for purchase and the cheapest I found was to search for "AquaClear 634 Impeller" on Amazon. The price was $7.30 plus shipping $5 in my case.)

History:

I have a freshwater 23l Edge, and I was interested in increasing the filter rate to keep the water very clear and to possibly increase the number of fish. I researched as many other people have whether other filters that were larger would fit in the standard Fluval Edge tank. (I was not very interested in modding the case and losing the lighting, or having an outboard filter.)

I downloaded the complete parts list for the AquaClear series of filters and noticed that the only part numbers that are different between the AquaClear 20 and the AquaClear 50 are the plastic housing (including the filter lid) and the impeller. The motor and the impeller cover are identical. That seemed odd because I was expecting the motor to be different. So since it was cheap, I ordered the 634 impeller.

When I got the impeller into the motor housing, I realized immediately why the impeller changes the throughput. The impeller blades are longer and are closer internally to the walls of the pump. (Very nice design; I can post pictures of the two impeller blades side by side in the pump housing to show how much wider the 634 impeller is.). This change forces more water through the pump for each rotation, and consequently a much larger volume through the filter.

Effects:
I notice the fish now have a current to swim against in the tank. I do not know if this is good or bad for the fish. Maybe someone can tell me.

I do not have live plants or delicate fish that will be hurt by the increased current in the tank.

The only downside that I have noticed is that because of the shallow depth of the 23l Edge, the fine onyx gravel at the bottom of the tank was getting pushed away. A small divot was being formed where the water was coming down from the top of the tank. I simply moved a stone decoration under where the water comes down and this dispersed the stream.

Hi surlyguy.

Interesting post.

I wonder if this is what Fluval do with the 46 Litre Edge?....ie just replace the impeller, but use the same filter pump as the 23 Litre Edge. Of course, I imagine the 46 L Edge will probably have a larger media cross-section/volume to cater for the extra waste products of more fish, so the 46 L possibly ends up with a similar flow rate to the 23 L.

I'd have to say an increased flow rate into the 23 L tank would concern me slightly because 1) the inlet pipe will definitely need to have the sponge cover fitted otherwise shrimp and small fish run the risk of getting sucked in and 2) that the waterfall effect pounding into the tank will be even more pronounced than it currently is - I usually have my pump turned down to minimum, since my Celestial Pearl Danios seem to prefer it that way. In fact I've been considering ways to change the lip design at the bottom of the sluice gate to guide the flow more across the surface of the opening rather than down into the tank.

I used to be a mechanical design engineer so I enjoyed reading your post and look forward to hearing more about how you get on with your mod and seeing the pics you mentioned.

All the best,

Ricky

Actually , they have a 46L set up at the LFS and the filter for the 46L is identical to the 23L. Same rate. Same fiter width.

I guess they figure that the maximum rate of 100gph is high enough to support the larger tank. (about 8 times per hour).

The following is the view of the impellers in the pump housing (impeller 634 on the left and the original impeller on the right). Notice how much closer the blades are to the outside wall of the pump on the 634 impeller.


The following is a sideview of the blades. Notice how much lonnger and wider the blades are on the 634 impeller.

Thanks for this - just found an impeller on ebay for £8 inc shipping to the UK!

Hi

Can anyone point me in the right direction to buy a 634 in the UK? I can not seem to track one down. Any ideas?

This is awesome! I was looking for some kind of filter "upgrade" for my 46l tank and found this forum . I find there seems to be areas at the bottom where debris just collects so maybe this will help with circulation. Also, with the longer tube extending to the bottom I think it restricts the flow a little. My local fish store sells the impellers so I'm going to pick one up tonight. I also noticed the aquaclear 70 uses the same motor, but maybe that's overkill.

WilkBoy wrote: I also noticed the aquaclear 70 uses the same motor, but maybe that's overkill.

The following table is from the AquaClear replacement parts pdf ( http://www.hagen.com/pdf/aquatic/Aquaclear_English.pdf )



Notice that the Impeller cover for the 70 is different than the cover for the 20/30/50. This is the part that covers the rotating impeller and fits into the main body of the filter.

It is unlikely that the impeller cover for the 70 fits in the smaller filter cases. Also, there is no guarantee that the impeller for the 70 will fit with the existing impeller cover from the 20.

While the 20 has a rating of 100gph, the 50 has a rating of 200gph, and the 70 has a rating of 300gph, the flow using the A-634 is certainly more than adequate for either the 23L or 46L.


In fact, I turn the setting to the lowest flow when I feed the fish to avoid suctioning up the food before the fish eat it. I know I can turn the filter off while feeding, but I am always afraid that I will forget to turn it back on afterward and kill some of my fish.

Good point! The 70 probably won't work.

Well, I grabbed the impeller for the 50, and it works great; definitely a noticeable change.

Does anyone know where online I can buy a Aquaclear 50 impeller unit that ships to the UK or alternatively Fluvals UK version of this impeller? Really want to do this mod!

I have just ordered the impeller . Shaft not included is the change over difficult? Any pointers. Thanks

Hi, I can't find the impeller 634 for the UK, can you help me please

Hi also do you know if the aquaclear power filter 70 would fit and is it worth upgrading

AquaClear Impeller 634 wrote:Hi, I can't find the impeller 634 for the UK, can you help me please

I just searched http://amazon.co.uk for "AquaClear 634 Impeller" and they have the impeller for 19.23 pounds.

http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=AquaClear%20634%20Impeller

AquaClear Impeller 634 wrote:Hi also do you know if the aquaclear power filter 70 would fit and is it worth upgrading

I checked the dimensions of the Aquaclear power filter 70 and it will not fit in the top cover of the Edge tank. The only simple option is to simply change the impeller as described.

If you are concerned about not having enough filter media you can possibly reduce or eliminate one or both of the other media in the three stage filter.

The stages are as follows: http://www.filtersfast.com/P-AquaClear-50-Aquarium-Power-Filter.asp

Stage 1) Mechanical filter - a course sponge to stop particles (Not terribly necessary in my opinion.)
Stage 2) Chemical filter - activated carbon to absorb impurities (Probably the most important stage)
Stage 3) Biological filter - ceramic beads to provide surface for bacterial growth (Possibly not needed depending upon whether you have live plants in your aquarium)

One option is to simply replace the 1st or 3rd stage with an additional stage 2 filter media. Just a thought.

I massive thank you for your help.

AquaClear Impeller 634 wrote:I massive thank you for your help.

Now that I look at the price comparison on Amazon.com ($8.00) and Amazon.co.uk ($30.00), it seems rather steep.

Is that the way it always is? I wonder if Amazon US delivers to the UK?

http://www.amazon.com/AquaClear-Impeller-Assembly-Power-Filter/dp/B0002AQDRW/ref=sr_1_1?ie=UTF8&qid=1366926648&sr=8-1&keywords=Aquaclear+634+impeller