# Pump failing! Fluval G6 low flow rate, then stopped



## sphack (May 2, 2012)

Before we start, don't knock/bash the filter selection. I have it, its not changing for this tank... (Basically it is a computer integrated with the filter. After all, my wife encouraged me to get the little guy  )

I have a G6 on a 75 gal tank. For those not familiar with this model, it detects filter flow and reports it. It has worked great for monitoring how full my mechanical filter becomes. Well, a few days ago, it started running 50% flow. I've cleaned out all the usual suspects - the mech filter, the inflow, the co2 reactor's (ext5000) foam block (the usual suspect), outflow - with no avail. 

I've taken nearly everything apart, cleaned out the goop from all the hoses (WOW! is that normal?) and still no increase. I did not clean out the hard plumbing with the co2 reactor because my brush does not make 90 degree turns very well.

Any ideas what to check?

I've already
* removed the chem filter
* cleaned (and swapped) the mech filter
* cleaned all tubes, inflows, outflows, hydor inline heater
* cleaned the impellers


Some experiments I still need to make:
* hook up the filter return straight to the tank bypassing the co2
* remove the biomedia
* re-clean the filter and figure out where the flow meter is...


I don't know at this point whether the flow is really at 50% or if the flow meter is incorrect. I do know that if I open up the drain instead of putting water back to the tank, the filter shows 100% flow...

Update: No amount of cleaning helped. This evening, it bubbled then stopped flowing all together! See posting 3


----------



## sphack (May 2, 2012)

Unfortunately bypassing the co2 setup didn't help things much. While I was at it, I changed the co2 plumbing and removed 2 ball valves, and 3 90 degree bends. 

Googling the topic it sounds like this is one of the problems with the g series. Will be contacting fluval on Monday.


----------



## sphack (May 2, 2012)

Urgh. After. CLeaning, recleaning, and research, nothing I do can get the flow back up. This evening it actually stopped flowing all together. I was watching a movie when it gave the last gurgling. The helpful computer stated that it had low flow. Really??!

I cleaned all the seals, including ones I've never seen before. After powering it on, 100% flow. After an hour 75%. Hopefully it will not die again overnight. 

Tomorrow morning I'll be on the phone with fluval!

I forgot to mention that the pump has been running for less than 3 months.


----------



## PlantedRich (Jul 21, 2010)

It may just sound irritating but I have a story to tell you. Check the directions carefully on how to operate the filter. 
I have a friend who got a great big nice Eheim electronic model for free. The former owner saids it was broken so gave it away. I refuse to take that answer easily so took a look at the problem. Somebody had been punching buttons without reading the directions. Once programmed and restarted, it is a fine filter. 
Would you be so lucky??? Worth a shot??


----------



## Maybe (Jun 27, 2013)

Any update about the G6 I have the same problem .


----------



## sphack (May 2, 2012)

I sent the top portion of the filter in to fluval. After they were trouble shooting it, they simply said it didn't work and sent me a completely new unit. I've been running the new one on a spare tank in the basement for I guess over a year now without any problems. Granted, the new tank is a non-planted tank so that might have made a difference. 

My main tank has an Eheim Pro (the big one)

A few observations about the design of this guy. 
* The non-bypassable filter does a good job, but you need to clean it often.
* They offer two types of filters. The fine filter is too fine, especially for a planted tank. I had much better luck keeping things running by swapping two normal/white filters every so often. 
* I like the way you can remove/add the filter so easily without detaching hoses
* The power on time of the computer is annoying (15+ seconds) when trying to purge out air bubbles from the impeller.
* The Fluval G5 is the Italian sports card while the Eheim is the German one. Both are good, the Italian one is great but finicky/quarky. The German one is over engineered and keeps going regardless of what you throw at it.


----------



## Rick91981 (Oct 25, 2007)

Maybe said:


> Any update about the G6 I have the same problem .



Maybe I can help some. I have the G3 and have had flow issues. I was able to fix it myself (so far anyway) by replacing the o-rings on the intake of the rim connector(see attached pic). In my case those were worn out and it was sucking in too much air. I replaced those and so far so good. Been about a month since I replaced them. Also be sure if you have a pre-filter on your intake that you keep it nice and clean.

Also when starting it, prime it a lot more than you think you need. I hit the button 7 or 8 times and it starts right up. Goodluck!


----------



## Clear Water (Sep 20, 2014)

Have you tried running it without any filter medium? Have you pull out the propeller or cleaned were it fits in? I don't know G6 but if it a pump problem it can only be few things that could be an issues.


----------



## michaelschneider (Aug 5, 2015)

Hey kids so I've been having flow issues with my g3 as well. The flow rate was down to 270l/h and it used to be more like 800 or 900 l/h. It was barely strong enough to get the water to start flowing through the filter. Like maybe 30-40% of the time I could get some flow going after power cycling the filter but it would be super weak, and the other times it would just cough and sputter and nothing would move through.

The Hagen customer support people (800-724-2436 in USA) suggested to clean and replace the impeller which I did with no improvement. Then I realized that the mechanical filter was really blocking the flow because when i picked it up it just held water inside. I have a planted tank so it kicks up a lot of dirt when I'm moving the plants and stuff. I scrub the mech filter regularly and replaced this one a couple months ago but it didn't help. Since there's no way to run the unit without a mech filter in place, I just cut a big fat hole in the side of it to see if that would isolate the problem.

Boom just like that my rate went back up to 890 l/h! The mech filter was too clogged.

So now I ordered a couple new mech filters and and some filter floss. I'm thinking I will just replace the nugget thingies in one of the bio filter trays with filter floss and just forget about the fluval mech filter. That stuff worked pretty darn well back when I was a kid. If I remember I'll report back here what happened.


----------



## Bronxfishguy (Aug 30, 2015)

*G6 flow problems*

You are the man !! I never thought of poking a couple of holes into the mechanical filter and then putting floss into it. Well done !!


----------



## randygsx (May 15, 2012)

Also ran into this issue with mine. Ordered some of this floss and I'll report the results for me soon as i get the floss.

Amazon.com : Blue Ribbon Pet Products ABLPLY14 Polyester Floss Bag Filter Media, 14-Ounce : Aquarium Filter Accessories : Pet Supplies


----------



## PlantedRich (Jul 21, 2010)

Funny how often the same problems get talked about even after years!
Anybody notice the time line on this problem? 

August 2012 to November 2014 and now we see it again in August 2015>

Some problems are never solved, they just lay dormant for a while.


----------



## randygsx (May 15, 2012)

So I finally got around to trying this. 2 water changes ago i cut slits in my filter every other fin with a box cutter and put floss inside. 

Result: water flow increased to 25%

Next water change (1 week later) i put in an uncut filter back in so that i still had an "unmodified" filter until i confirmed that this mod would benefit the tank.

Result: water flow back down to < 10%

After cleaning the modified filter, I took the box cutter and cut a TON of slits in the filter this time. Added floss then installed it into my filter with today's water change

Result: water flow increased to ~33%

So michael is spot on with the fix. Looks like the design of the water flow with the G6 is as follows:

intake -> prefilter -> baskets -> carbon/purigen filter -> outflow

Since the prefilter is really fine, it clogs up really fast. Especially in a planted tank.

Most filters take the water through coarse filtration and doesnt pass the water through fine filter media until the very end.


----------



## Plantednoob7 (Feb 4, 2016)

So the saga continues years later... 

I have been very happy with this filter for the past 23 weeks it has been running. Last night I decided to clean the impeller because it looked like it had a lot of gunk. After cleaning and putting filter back together flow reading was down to like 25%. It's usually 100% after I clean my merch filter. 

I quickly ordered a new impeller on Amazon with 1 day shipping as I have discus and lack of filtration worried me. I installed new impeller and still same issue. 

I thought maybe flow sensor is bad but when I put my hand in front of spraybar flow is obviously diminished. 

I have never had the issue of mech filter not giving enough flow. That's prob because I clean mine with a garden hose and pressure nozzle. I do that once a week and flow stays at 100%. 

This problem is entirely different and I can't figure out why. Is it coincidence that it just happend when I decided to remove impeller? 
Is this the common issue between all problems? 

Who knows but I sent fluval an email. I hope they replace this expensive filter. 

Should a just went eheim


----------



## PlantedRich (Jul 21, 2010)

Filter flow is an old issue but still a current problem so worth the space to discuss!
I'm one that thought I understood the way flow worked until I got a new issue a few weeks back. The flow was good when I restarted and all was fine for a day or so and then went bad. I cleaned and looked for leaks and all that. Looking for air in lines is much easier when not dealing with a black tube! I can look in my tubing by shining a bright light through it and I could see no air coming down the intake but there seemed to be small air bubbles going up the output. Pretty new filter but I changed out the suspect seals and got no change. 
What I did find was not found by looking but found by checking my logbook. I log weird little details like when I change out media and if I use a different type. BINGO!
I had used this filter for several years and only rinsed the old soft media until it got thin enough to be a pain to straighten out to lie flat in the tray. I swapped it out for the DIY media that I now use for almost all filters. It works well on most things and I have a ton of it. 
What I found was the media is light enough to lay flat for some time, making me think all was well but at some point it begins to float. Water flow is bottom to top on canisters making floating a definite possibility. When it floats it can go up and wedge itself tightly against the hope where water is sucked into the pump to go back to the tank. Like an upside down cork in a barrel the flow stops!! 

I now suggest that it is a good idea to ask where the media is when you have a flow problem that is not caused by dirty, leaks or bad impellers. Funky intermittent things are hard to find. Especially if the media looks good until you close the lid and can't see what it is doing? 
An eggcrate "screen" on top of my soft stuff now holds it down.


----------



## Plantednoob7 (Feb 4, 2016)

It's strange. Haven't changed any media since this problem occured. I had only removed impeller to clean and that's it. I am using matrix and denitrate in the baskets. No fluval media. I have yet to here back from fluval. From what I see they sometimes replace the tops on these things. 

I have an eheim pro 4 600 slated for delivery Monday. Hoping fluval will replace the top on the g6 and I can sell it to at least cover the cost of the eheim or just save it for a backup


----------



## vvDO (Oct 18, 2010)

How's the flow if you remove all media?


Sent from my iPhone using Tapatalk


----------



## Plantednoob7 (Feb 4, 2016)

Setup the eheim pro 4+ 600. Wow what a difference. This thing moves some serious water. I know it's larger than what I need for a 75 but would rather error on the larger side for filtration. I cannot believe the G6 is rated for 90-180 gallons. It was barely strong enough for my 75. I actually had to throttle my pro 4 down to nearly 50% since I have discus. 

As far as warranty for the G6 fluval tried to give me some excuses but finally agreed to warranty. In the meantime I had contacted Amazon whom I bought it through. 

Wow that was easy! Amazon is sending a replacement one day shipping... No questions asked


----------



## PlantedRich (Jul 21, 2010)

If you get time before sending it back or whatever, it would be interesting to know if there is any part of the media which shifts so that it blocks flow. I don't like the Fluval tubing as I can't see through it to tell if there is air passing. But then it might be really good info to remember if we could find out it was as simple as media floating or some way blocking the flow.


----------



## Plantednoob7 (Feb 4, 2016)

PlantedRich said:


> If you get time before sending it back or whatever, it would be interesting to know if there is any part of the media which shifts so that it blocks flow. I don't like the Fluval tubing as I can't see through it to tell if there is air passing. But then it might be really good info to remember if we could find out it was as simple as media floating or some way blocking the flow.


Hey Rich I'll try and do that before boxing it up for return. The replacement one came today but I am going to stick with the eheim

Ok Rich 

I have it currently running in a 5 gallon bucket... 

I have 2 media trays full with one empty. The flow is now reading 100%. I tried empty tray on bottom was reading about 90%. Empty tray on top 100%. Thing I do notice though is at 100% there is a small whirlpool in a 5 gal bucket. I would expect much more. I assume the flow is reading 100 due to lack of media. It obviously expects a certain baseline of a filter full of media. I don't really want to waste any media to fill in that last tray... I used what was in that 3rd tray to seed my new filter


----------



## Dazeuponme (Aug 9, 2016)

Somewhere I saw that someone posted that they replaced the motor with a better one and a few mods it was able to work in the G-3. If anyone knows where that thread is I would love the link!


----------



## Plantednoob7 (Feb 4, 2016)

Dazeuponme said:


> Somewhere I saw that someone posted that they replaced the motor with a better one and a few mods it was able to work in the G-3. If anyone knows where that thread is I would love the link!


I replaced the G6 with an eheim. Couldn't be happier


----------



## Triekc (Aug 20, 2016)

*Fluval G3 and G6 Issues*

I purchased Fluval G3 and G6 and after short period of time encountered issues leaking from the bottom and low flow rate. Regarding the first, i replace everything except hoses, leaks continued. Fluval support shared that the cause was likely inline heat and CO2 diffuser. Funny thing about that, those inline devices were on the lines for 3 months with no leaks, suddenly, over night, both pumps leak when hooked to that line. So, removed all inline devices, repurchase tank heater/CO2. Pumps have not leaked for few days since the change, fingers crossed. I am certain i was told before purchase of the Fluval that inline heater would function fine, but after leaks started, support told me Fluvals were not engineered to have inline devices, and that no one from their org would have told me this, umm, i guess i am going crazy. This important fact is not presented on Fluval's website. Regarding the 2nd, i have these pumps on 55 gallon tank. Both pumps claim to be sufficient for this size tank, and in the case of the G6, much larger tanks, so i purchased thinking i would have vigorous flow inside the tank, something i desired. But not the case. The G3 flow is trickle, G6 is what i would think the G3 should be. I was expecting a serious flow that would cause plants to move, fish to fight current, but not really the case.


----------

