Fluval Flex Filtration Flaws?

Chrisv.

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Yeah, I think this would be fine for freshwater but they missed the mark for saltwater. Superglue might work if I can’t get the custom made overflow blockers that someone mentioned earlier. Thanks for that idea!
My experience with the stock hood on the flex is that you NEED extra airation. There is just not enough gas exchange. When I put an airstone in the tank I saw a NIGHT and DAY difference in the health of the tank. I can't stress this enough. An airstone (as unpopular as they are in modern. Reef tanks) also provides sufficient surface agitation to break up films.

It doesn't have to be horrible or unsightly. I have the stone 2.5 inches below the water line in the back corner just under the return. It does not release microbubbles.

This was an overnight change for my flex. I've never used an airpump in a reef before this, but on the flex it was an absolute game changer.

Give it a try!
 

DaddyFish

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The look of the tank is what sold it for me! My husband loves having it behind his desk & if not for the filtration issues, I would like it as well. If I remember correctly, the stock pump has somewhere around 245 gph output, so I could definitely increase that. I will try the method you’re suggesting though just to see what it actually does.
I'm very sorry, I typo'd the gph. It should be 250-350 gph.
 
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Brit’s Fish

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My experience with the stock hood on the flex is that you NEED extra airation. There is just not enough gas exchange. When I put an airstone in the tank I saw a NIGHT and DAY difference in the health of the tank. I can't stress this enough. An airstone (as unpopular as they are in modern. Reef tanks) also provides sufficient surface agitation to break up films.

It doesn't have to be horrible or unsightly. I have the stone 2.5 inches below the water line in the back corner just under the return. It does not release microbubbles.

This was an overnight change for my flex. I've never used an airpump in a reef before this, but on the flex it was an absolute game changer.

Give it a try!
I have an extra air pump that I just bought for the reef glass skimmer. I’ll try that tomorrow!! Thanks for the tip!
 
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Brit’s Fish

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Thank you all for the awesome suggestions! I wish I had known what an issue this would be with this particular tank & I have looked through the forums but hadn’t been able to find anyone really talking about it. It does make me feel better to know I’m not the only one who noticed/experienced this. I have 4 other tanks that are doing great and this one having this issue & not being able to solve it has been a little depressing. 4 out of 5 ain’t bad though, as they say. I’m going to give all these suggestions a try, one at a time, before I decide to just chuck the whole thing! Lol
 

Chrisv.

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Don't chuck it! They are cool little tanks! I modified the lid on mine to hold a kessil 360we and use a mp10 for flow. They are something a little different.

FWIW here is how I have my back compartments configured (from L to R): chamber 1 = mesh bag of ceramic bio media, in-tank filter pad going all the way from top to bottom agains the chamber 1-chamber 2 interface, chamber 2 = nano UV sterilizer, bag of high density GFO, bag of ROX carbon, chamber 3= heater and return pump.

(i'm using the medium size one. 15 gallons i think)
 

homer1475

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After looking at the pic the OP posted, I can't see how that filtration actually works? I also do not own one of these.

If there are grates at the bottom where the "return" pump is located, how is it drawing in any water from the top into the filtration? It seems to me that only the bottom grates draw water in, and then just pushes it back out the return pipes?

Looks like quite a bit of the issues would be solved by just blocking off the bottom grates.
 

Chrisv.

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After looking at the pic the OP posted, I can't see how that filtration actually works? I also do not own one of these.

If there are grates at the bottom where the "return" pump is located, how is it drawing in any water from the top into the filtration? It seems to me that only the bottom grates draw water in, and then just pushes it back out the return pipes?

Looks like quite a bit of the issues would be solved by just blocking off the bottom grates.
Pretty sure the pump chamber is more isolated than it looks in the diagram. I have the tank that's one size smaller and there is no mixing in that one.
 

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I have the same tank and it has been up and running for about 14 months now. There is a guy that 3d prints bottom intake guards that fit into the grates at the bottom, google 3Deep and should find his facebook page. Only issue is that he is in the UK so took a couple weeks to ship. I still have some issues from time to time but my tank is also pretty heavily stocked. I did finally try a skimmer starting about a month ago and I can't tell if it has really helped or not, so I cut it back to only run at night.
 

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Not sure if has been suggested already, but since I have a Flex 15g and the 32g, the first upgrade I made was to steal the return nozzle from the flex 15g and put it on the 32g. It gives a bit stronger flow, can be aimed and bent into better positions, and provided a bit more agitation on the surface. If you don't happen to have a flex 15 around, the nozzle costs ~$5 on amazon.

I did later switch to a canister filter due to the noisy return pump though, ymmv. There is also an owners thread for this tank on R2R where people shared what mods they made to it, most people seem to love the custom baskets.

 
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Brit’s Fish

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Not sure if has been suggested already, but since I have a Flex 15g and the 32g, the first upgrade I made was to steal the return nozzle from the flex 15g and put it on the 32g. It gives a bit stronger flow, can be aimed and bent into better positions, and provided a bit more agitation on the surface. If you don't happen to have a flex 15 around, the nozzle costs ~$5 on amazon.

I did later switch to a canister filter due to the noisy return pump though, ymmv. There is also an owners thread for this tank on R2R where people shared what mods they made to it, most people seem to love the custom baskets.


Yeah, these are definitely longer than the ones that come stock on the tank. Hadn’t even thought about this!!
 
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Brit’s Fish

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If it works, don't change a thing!
Agreed! If it ain’t broke…
I threw them out because I didn’t like having about half of the water bypassing the carbon, but since I’m having issues anyways, I’m probably not the best person to give advice on this tank. Lol
 

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Agreed! If it ain’t broke…
I threw them out because I didn’t like having about half of the water bypassing the carbon, but since I’m having issues anyways, I’m probably not the best person to give advice on this tank. Lol
meh we're all kinda winging it with the Flexs' it seems
 
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Brit’s Fish

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Did you have any success in turning the nozzles vertical? My surface film is 99% gone already!
It does help some but since it’s only been a day, I’m letting it go for another day or two before I really judge anything. I am also going to upgrade the pump to the Sicce 1.5 today to see if more flow helps in this endeavor. I think the stock pump is just weak. I upgraded the pump on my Evo almost immediately & got great results there. Not sure why I would think this tank would be any different but I also don’t have any corals the require a lot of flow in the flex.
 
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Brit’s Fish

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meh we're all kinda winging it with the Flexs' it seems
Yeah, I always joke that the only thing left in my Evo that’s still Fluval is the glass. It’s an awesome tank but everything that came with it has been chucked or repurposed. I’m using some of the foam filters from it as a silencer for the skimmer on my 150g. Lol
Edit: it sounds like my Flex is going to end up the same!
 
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