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Fluval 405 Problem...internal Flow Backwards?


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Anyone else with a Fluval canister come across this issue?

Mine seems to be flowing backwards internally, but it's still sucking in through the inlet, and pumping out through the outlet.

Here's what tipped me off. I usually put one or 2 of the Fluval micro polishing pads into one of the trays. Traditionally, when changing them out a few weeks later, they would be "clean" on the upper facing side, and "dirty" on the bottom facing side. Makes sense, because the Fluval flows through the big sponge filters first, then down to the bottom of the canister, and then thew water flows upward through the bio media and all the trays, and out the top past the impeller.

Now, I'm getting lower flow volume (my spray bar doesn't shoot water as far any more) and the micro polishing pads are dirty on the top side......indicating to me that the water is flowing down through the trays.

It's also become a PIA to prime, even when I fill the entire canister prior to putting the lid on, and then pour in a little more water into the top, prior to putting the hoses on. Takes forever, to the point that sometimes I think it's not going to prime unless i remove the hoses from the side of the tank, fill them with water, and turn it back on.

I've replaced the plunger and rod for the primer........no change. Replaced the cover for the impeller area.......no change. Took the impeller and it's magnet thing out and scrubbed all the sludge off the magnet thing, and scrubbed out the sleeve in the motor housing that it spins in and that seemed to up the flow rate slightly.

I'm wondering if the lid that fits onto the top-most media tray, that has the collar that's supposed to seal against the motor housing/impeller cover, is not sealing well? So instead of getting really good suction from the impeller housing, I'm getting an internal leak and water is sort of just flowing around where ever it wants?

Sorry for the long read. Hope someone can offer some advice.

I actually wouldn't mind going to a larger/better filter, but at the kind of money they go for, I'd like to run the bag off this 405 first.

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I think I may have solved the problem.

I ordered a new media tray cover via ebay, and then decided to play with modding my existing cover.

First of all, I've been noticing that the cover is bowed downward, away from the lid and the impeller housing that it's supposed to press against/seal against. It is just thin flexible plastic, and the way they have the reinforcement ribs under it, there's just no way to keep it from being shoved downward, and then being permanently bowed, as the 405's motor housing get's snapped into place.

So, I got the lid super hot in hot water, and while it was soft and plyable, I flexed it back into a normal flat position. Once cooled, it stayed there, but of coarse that's not a cure. Then I used 2 rubber o-rings (available in the plumbing dept. of any hardware store) and slipped them over the outside of the round collar, that's molded onto the of the media tray cover. They stacked up nicely, and were just slightly taller than the collar. My theory was that if they provided a better seal, the pumping action couldn't sneak past the collar, and would have to go down, through the foam, and the up through the media trays.

Everything snapped back together normally, and I'd pre-filled the filter with treated water. So far, so good.

Hooked up the hoses, plugged the filter in, turned on the power, and it instantly primed itself and immediately began working!

One more little mod that I forgot to mention: I used a pair of fingernail cuticle nippers to cut out some of the grill-work in the outlet opening of the media tray cover. I know the grill-work is there to keep large stuff from getting into the impeller, but I don't have any small stuff, either in the tank, or in the media baskets.......so I'll take my chances, vs. having much better flow.

I'll post back with an update and let you know how this works out after a few weeks of run time.

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At $200-something to replace this one, and another hundo+ if I went for something larger/more advanced, I had a bit of motivation.....if you know what I mean ;-). Plus, I've got a large kit of different size o-rings, so it was a freeby.

That said, the company needs to address this. The lid either needs to be thick enough that it doesn't bow down, move away from the impeller housing and create a lack of correct flow, or they need install a compressible sleeve like I've created, out of silicone, and supply it as part of the kit-of-parts that comes with these units. And they can say that they found out about it first, here at Kokos!!

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LOL. I've only used HOBs until last month, when I got a small Eheim Ecco. I'm really happy with it so far. I'm looking into the FX5, but that one's a lot more intimidating looking than the Eheim lol

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The 405 at 340gph is the only filter I have on this 70G with these 3 monster single tails. All 4 trays are full of Fluval's bio media ceramic cylinders, and in one tray, I'll put the micro polishing pads in on top of the cylinders. Once in a while I'll put in a bag of charcoal that I make up from bulk. In the opposite corner, drawing off the bottom through a section of Fluval pickup tupe, I've got a Rio90 pond pump...just to circulate water from the bottom of that area of the tank, up to the top where it can exchange CO2 for O2. About 44" of Marineland bubble stick (2 sticks linked together with a short piece of pvc tubing) is burried under the gravel at the base of the back wall and powered by a Tetra Whisper 60 so I get large tumbling bubbles. That's it. The water is always clear and I've never had green or white tinge, even with the tank in between 2 huge windows and getting quite a bit of morning/late morning direct sun.

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Well, I'm certainly a huge violator of that rule, as well as the gravel rule.

Although based on my little yearly bout with fishy illness, 2 years in a row now at this same time, I may not be a poster child. I may have brought that on myself though by getting waaay lazy with the water changes.

Now that I've (probably) got the flow issue solved, I might go back to using Sea Chem De-Nitrate granules in the Fluval. I'd be nice to keep those levels lower. Was hoping plants would help, but I don't heat the water, so that seems to keep the plants from growing, and these single tales eat everything, including Anubias Nana with those crazy stiff waxy leaves.

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Got an email from Hagen, makers of the Fluvals.

We thank you for taking the time to contact us.

The polishing pads you can only use for approximately 10 days then you need to throw them away.

Be sure you have all media in the correct baskets stated in your manual.

You should not have any poly fill, chemi pure or purigen.

Thank you,

Elaine Boyce

Customer Service Dept.

Rolf C. Hagen (USA) Corp.

I didn't mention leaving my pads in for extended periods, or using poly fill, chemi pure(whatever that is) or purigen(whatever that is). Nor did I mention having things in the baskets in the wrong order.

Just told them I'd found a problem with their filter, had come up with a solution, and invited them to contact me if they wanted to discuss either.

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I think their is a statement like that on the box of pads. I've left them in longer and had no issues with flow. They come out goopy green, so they really pick up a ton of stuff......but she just skirts my entire point. THE PADS ARE GETTING DIRTY ON TOP.......and that's not possible if the water is flowing in a counter-clockwise circle from the inlet on the left, down and then up, to the outlet on the right.

See the raise round "ring" that's molded into the top cover, on the stack of media trays? That ring is what is supposed to seal against the flat surface of the impeller housing....with no gasket. Being always shove downward, makes that cover sort of cave in, into that top media tray. As it caves in, it stops sealing against the impeller housing. My gasket of 2 o-rings compensated for the problem of the lid caving in. Below is a close up of that cover and the outlet port with the grill-work. My o-rings fit around the outside of the plastic ring surrounding the grill-work.

41eSFhI-FGL._SL500_AA280_.jpg$(KGrHqUOKiUE33UUzvE0BOG1(oJTZQ~~_35.GIF

Edited by austinado16
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I agree that O ring is definitely needed. Somehow I see this addition in forthcoming designs. May be they just don't want to admit fault to you... (shrug)

Good thing you were able to fix the filter though.

I'm glad you brought this up, as the 405 has been a model I've been considering. I think now I'm leaning more toward the FX5, which is a monster :D

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There's a Hagen/Fluval produced video on youtube showing how to set up, use, and clean the FX5. There is also one for the 405. Might be worth taking a look at both and see which is more user friendly for you. IIRC, I looked at the FX5 video last year and wasn't feeling the love. Can't remember why. Guess I need to go watch it again.

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Lol. That's probably why I'm still on the fence about getting it. It's not that I have unlimited funds for fish, but money isn't the consideration here. I just haven't quite found the canister that I totally love.

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I didn't know anything about them when I started shopping, and initially, it was for my new-to-me 30G. I went over to the local petbox store because I didn't want to wait for an online purchase to arrive, or have an umpteen week hassle if I returned it because it was a POS.

I looked at the most expensive Fluval and the most expensive Eheim, took 'em out of their boxes to look at how they were built, compared the size of the filtration, and how much media they held, and the simplicity of the build quality. I didn't want something all wizbang that would break some fitting off at the least opportune moment, umpteen months later.

To my rookie eye, the Fluval was better. I'm still happy with it. I think you'd like one.

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Thank you. That recommendation actually weighs a lot. It think my fish are getting a big canister for Christmas lol.

The FX5 is $212 on Amazon. That's pretty reasonable, I think.

Edited by dnalex
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If the hoses are coming off the valves on the canister, you may not have them installed correctly. You really have to shove them down onto the barbed fittings all the way, and then tighten those big plastic nuts by hand, so they are pretty snug.

Yes, if you're using the water polishing pads, I'd change 'em at least each month, if not sooner as Fluval suggests. They come 6 to a box I think, so you've got plenty on hand. Once they get all packed with gook, they're probably a major restriction to the flow in gallons per hour.

Also, a little tip on filling the media trays. If you stack your Bio Max cylinders, standing upright, in rows, and fill the bays that way, you'll be able to fit a lot more into each bay than if you just pour them in, in a pile. It's a huge difference. With Goldfish, you want all the bio media you can get your hands on! Plus, if you're trays are currently full, stacking will free up some space and you could drop in a bag of charcoal/carbon every once in a while, and even run a bag of SeaChem DenitrAte (change it out every couple weeks, just like you'd do with charcoal/carbon).

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Sounds like the valve assembly is not being locked in place by that silver paddle-handle latch. That latch has a thin curved "claw" on the underside. With the valve assembly turned off, and the filter turned off (unplug it) lift up on that silver paddle handle and inspect that claw. You may find hat it's snapped off because that valve assembly can't be lifted out of the Fluval's lid, if that claw is in the lock position with that paddle handle down.

The good news is, the valve assembly can be purchased seperately, via ebay or Amazon.

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