Fluval Fx5 Modification

Introduction
So as we all know the Fx5's design is not the very best for media capacity. I have been thinking of ways to improve this and some ways have been modifying the baskets but this would be way to much work and would still yield little increase in media capacity.

So I though, why use the baskets? They are only there to seporate the media and for ease of cleaning for the standard consumer. They are also to help with the air purging as well...

The modification that I have done has increased the bio capacity from 5.9L to 12 Liters or more. This is with 4" of mechanical foam. This increases to about 14 Liters when using only 3" of foam.

I use 4" of foam so I only have about 12L of bio media.

This modification is good for a few things.

1. ) Increase bio media capacity. Possibly around 12-15L
2. ) Decrease velocity of water flow for more contact time with bio media
3. ) Large area for flow which decreases the flow restriction.
4. ) Should help increase flow output since the water only has to change direction ONCE instead of THREE times.
5. ) Cleaning should be even easier and you will not need to remove bio media to clean the spunges like you had to before.
6. ) Eliminate about 5 possible warn o-ring issues
7. ) Original Foam blocks don't seal as nice as I would have liked to the basket above.
8. ) Increase the time between change intervals. In original form if you had fine filter foam in the center baskets, they could clog up real quick causing a drastic decrease in flow and lots of cavitation of the impeller and you would get LOTS of air bubbles everywhere. Should be able to use fine filter pads for longer periods of time.
9. ) Due to the decrease in flow resistance, hopfully this will help with the cavitation problem in the Fx5.

I may think of more reasons but so far this seems REALLY good.

Here are some updated figures;

Unmodified Fluval Fx5 Stats
Media Capacity: 5.9 Liters (im going to measure this since I think its wrong too..)
Mech capacity: 294 sq in; 369 cu in; 6 Liters
Measured Flow Rate: 525 GPH
Max Head Height: 3.3m (10.8ft)
Filtration Volume: 11.2 (Hagen says 20L. I call BS)

Modified Fluval Fx5 Stats.
Media Capacity: 12 - 14+ liters. (Depends on depth of mechanical filtration)
Mech Capacity: Est 108 sq in surface area. 325 cubic inches; 5.3 L (2" prefilter foam and 1" fine filter foam.)
Filtration Volume: 19.3L
Measured Flow Rate: ??

Ehiem Statistics
Eheim 2080 Media Capacity: 12 liters
Eheim 2080 Estimated Mech Capacty: 1.5L; 92 cu in
Measured Unmodded 2080 Flow: 318 GPH
Max Head Height: 2.2m (6.6ft)
Unmodded Filtration Volume: 13.5 L


Construction
The new design needed to be carefully thought out. I wanted the increased in bio capacity but also wanted a good amount of mechanical filtration. I wanted to increase area for increase in flow as well as an increase in volume for increase in media. I had to design it so the air purging could still work the way it should which took some rethinking and redesigning.

I used egg crate as seporation trays instead of the baskets and I order sheets of foam and custom cut them to fit for a 100% bypass free seal.

Im using Bio Bale as my bio media instead of the Fluval Bio Max which I have had great success with. The bio max would be way to expensive for the amount I need compaired to the bio bale which has TONS of surface area.

I had to keep the intake pipe submerged in water while the pump shuts off so the purging can work the way it should. I did not want the air to travel back through the intake. Only wanted it to go through the output. So I had to make a "pocket" for the intake pipe to sit into. This will also allow for a 180 degree dispersion of the water intake flow.

I had to lower the top tray to keep an inch of gap at the top surface so water can flow. Otherwise the top cover will seal against the spunge. Now the filter holds about 11.9 liters of bio media. I could cut the 2" spunge in half and get back up to 13.7 liters but I think it will work just fine.

As large as the Fx5 looks, the inside doesn't have much space to work with

Here is how I setup the egg crate.



In the pictures above you don't see the pocket I made out of a 3" PVC cap that I cut to a snug fit with my band saw.

TEST RUN #1

I hooked the filter up and did a test run.

It seemed to have worked pretty good. The system had purged a lot of the air out through the output on its own. Flow seems to be the same as before.

One thing I have to look into. The canister will not purge 100%. Air is still trapped inside all the time for some reason. Even if I shake the filter and tilt it about 50 degrees to the side no air comes out.

I removed the lid and started looking at the filter foam. I noticed there was a bunch of small air bubbles forced into the coarse foam right where the jet of water comes from the small air purge tube.

So I thought that maybe the air was getting trapped in the media. I started lifting up the coarse foam and noticed no air trapped under it. I than lifted up the fine filter pad and noticed a few small bubbles surfaced. I also then lifted the very fine pad and one good sized air bubble surfaced.

I removed the fine filter pads and kept the coarse pad in and im still having a problem with air.

Im going to try without any foam to see what happends.

I havn't checked but possibly the tube is getting clogged......

Im really going to look into this as far as my knowledge will let me.

CONTINUED OBSERVATIONS THRU THE NIGHT for TEST RUN #1

Within an hour all the air has been expelled. Most likely worked out by the impeller. There is no longer air in the canister. This is only with the coarse spunge and I would imagine that with the fine spunges the air would not be able to get worked out as easily.

Flow is right up there. I think its a bit more than before but this could heavily be due to the dirty filter fiber reducing the flow in the Fx5 I was running before.

Its been running overnight without any issues so far and is as quiet as it was before.

Overall im very please with how this turned out as the filter works as planned and is very very quiet like before. There is just a small bug I have to squish in the new design.

I think it might be really neat to cut the center portion of the cover out and silicone or hot glue or PVC glue some clear plexy glass/lexan over the top so I can see what is happening

My Bio Bale has come in so im going to be putting that in later on today since im at work right now.

While switching out filters and allowing the modded filter purge it loosend up a lot of junk in the hose which was thrown everywhere in the tank. The filter picked it all up and held it in either in or on the coarse spunge. Before I removed the fine spunges they too seemed to pick up a lot as well.

So far the general function of the filter seem to be exactly what I wanted.

I may try to increase the inner diameter of the air purge tube but I would rather not have to do this since that would decrease the output further. It may not be anything I would be able ot measure though so I may be alright. Increasing the ID of the tube I would think may help with purging the rest of the air. Thats as long as the air is reaching the tube.

I know installing a bulkhead at the top of the canister will solve this issue but that seems like a quick hack instead of a fixing a design flaw with the moded filter. So with that said, the tube should do its job.

Well I tested my other Fx5's purging with no baskets or media in it. It seemed to have purged 100%.

This leads me to believe its a pressure differential issue possibly. The only difference is that the tube in the this Fx5 was long and extended to the bottom.

This seems to be the only difference compaired to my modded Fx5.

I've never looked inside an FX5 first-hand, but the baskets are there for a reason - the water usually flows down the solid sides of the baskets on the outside, and then up through the insides of the basket, through the pump and out again. With no baskets there to channel water, what iss making the water go through the media, rather than dropping in and just going right back out again? Maybe I'm missing something here.

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Actually you have it backwards.

Water come from the intake tube which reaches to the bottom of the outside of the baskets, the water than travels up and through the foam and continues up to flow back down thru the center of the baskets which meets up with the pump to pump the water back up again. The way you were thinking, the water would never reach the pump since the pump is on the bottom and not on the top.

With the modded design, the intake is submerged into the PVC pocket I put in on the side. That water flow than travels up the pocket and spreads along the top surface of the coarse filter foam and travels down through 2 more layers of fine foam and than travels down through the bio media and than meets up with the pump to pump it out.

I just recently checked the media and it its working perfectly. The water is crystal clear and the filter foam (coarse, fine and very fine) are capturing a lot. The filter is 100% bypass free since all the foam is cut to fit snug up against the inside walls of the filter

There seems to be some confusion as to how the water flows in the Fx5 after its modified so for those of you who are not so sure I did a quick sketch and here it is.

I recently today opened up the filter to see how it was working and it appears to be working great! No bypass, everything is being filtered as planned. YAH!

The canister purges about 98% but there is always and forever will be some air trapped inside at the top which does not effect the filtration it seems. The air does not get tossed around either so through the multiple starts and stops and multiple purging times the filter always ends up quiet within 30 minutes to an hour.

The great thing about this setup is that I will never need to remove the bio bale for any reason. All the mechanical filtration is right on top.


Filter break down process I use;
1) keep filter running
2) close intake and pull intake off slowly to allow the filter to start sucking in air.
3) allow filter to pump out some of the water into the tank with the intake valve removed. (Watch your aquarium water level!!)
4) close output valve and unplug the pump
5) remove output valve and remove filter.
Not a drop of water should be spilt while removing the valves using this procedure. Hagen obveously didn't think of using this procedure since they say to use a rag to catch the little spill of water that you will get when removing the valves.

would put nothing but LR in there. i could see mine tank with alot more filter feeders increasing without those sponges and carbon. i like more nature filter than man-made filters. the only man-made filter im using is skimmer.

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Lava rock has less surface area than bio bale.

I do agree with you for salt water application about using natural filters. I originally wanted to post this in the "freshwater" section since its more directed toward that area but I screwed up while posting. **** us newbies.

If your having problems with Air bubbles purging how about filling the canister with water before and soaking the foam elements while squeesing out the air bubbles then put the lid on.
I just cleaned out my Fluval 205 canister filter for the first time and fould out the middle basket has 2 levels and bags of charcoal.LOL!!
I only opened up one bad and the other one was still in the plastic wrapping!!.No wonder I thought the flow wasnt that great.HAHA!
Ok well now after cleaning up the Foam elements I saw room for improvement in this canister also.
There is always room for improvement and having a clear wondow to see everything is great also.I have seen a few canisters that were clear.They should always come clear.

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It doesn't matter how you do it. You are supposed to fill the canister with water first. Atleast 2 gallons. I would reccomend doing this as well since if you have it fill up when its empty, assuming your hoses are full of water, the water level in you tank will drop quite a bit. My 55 drops about 1.75" hehe.

Theory Testing Continued
So I have done some more testing and thinking and I may have figured out why its not purging 100%.

I do not believe it to be the intake tube length at all. I could not make this jive with the issue at hand and I tested the empty Fx5 once more and came up with the same results as I am having with the modded Fx5. Its not purging 100%. No matter how many purging attempts you give it, not all of the air will escape. Some may, but not all. I just happen to get lucky the very first time I tested the empty basin. I had to give it about 5 or 6 purging attemps to get the air out the first time. This time I couldn't get all the air out.

So after looking at the baskets for a while and looking at the cover I believe the succesfull purging is due to the reduced area in the center of the baskets causing a large air bubble to form in a more condensed area to allow more of the air to be expelled at one time.

There are many areas under the cover that can trap air easily. The area has not be enlarged to a much greater area than what is available with the center of the baskets..

My idea is to reduce the total area and allow only a 3" - 4" diameter area for all the air to drop into. The area on the outside of this 3-4" circle will be angled upward to force the air into the center. This is how the top cover is designed naturally but with all the areas for air to get trapped in now its not working to its original design.

More will come