Fluval Flex 32.5 Heat Issues

Lsuhunter

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I have had my Fluval Flex 32.5g tank set up for about 7 months now and always battled heat. My tank ran in the 81-82 degree range and actually did fine, but I finally decided to get the heat under control so I can start trying some more finnicky corals. I got the idea to add PC fans to my rear lid compartment from people on here and wanted to document what I did for others with this tank.

I first ordered an inkbird temperature controller and 2 pc fans found on amazon.



The PC fans come wired together and if I were to do it all again, I would consider buying 2 single fans that can connect together so I could test using just one or different speeds. One fan over the middle chamber may end up being enough but I will never know now. But they work fine as expected and were cheaper than buying 2 individually.

To start, I took the back chamber cover off and marked exactly where I wanted the fans to sit. I tried to pick the flattest spot so the fans would sit flush, I then drilled a pilot hole to mark the center. After that, I used a 3 inch hole saw drill bit and cut out the 2 circles using the pilot hole.
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Next, I took the screws and cage off the bottom side of each fan. I tossed the cages to get the fans to lay flat and marked the screw holes with the fans centered above each circle. I drilled out those 4 holes on each to make attaching the fans to the top easier.
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Finally, I inserted the screws from the bottom of the lid holes and attached back to the fans to hold them in place.
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One of the major positives about this tank and the tight fitting hood is the basically zero evaporation. I wanted to try and keep this evaporation minimal so I do not have to buy an auto top off. So I set my inkbird to 78 degrees with a 1 degree cooling differential. The way the inkbird works is that it does not start cooling until this 1 degree difference is met. So when the temp hits 79, the fans kick on and cool the tank all the way back to 78 before they turn off. I tried it with 77 and also a 2 degree differential but the fans were running more than I liked and causing more evaporation. I am getting slightly more evaporation now but nothing that water changes or adding a small bit of rodi water once a week doesn't take care of(less than 1/2 gallon a week).

I have been very fortunate to have a healthy tank since the start that even went through a 3 day power loss during a winter storm in February. Even though I lost a lot of coral during that, my tank immediately bounced right back which was a nice surprise. Here are a few shots under mostly blues that I run and a few with whites turned up.

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KingTideCorals

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Well done! Heat issues can be an issue in reefs for sure! Love how you integrated the fans directly into the system! DIY skills off the charts! Loving it!

This can be a really helpful thread for anyone else dealing with this exact problem with this tank! Thanks for the write up!
 

Reydin

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Well done! Heat issues can be an issue in reefs for sure! Love how you integrated the fans directly into the system! DIY skills off the charts! Loving it!

This can be a really helpful thread for anyone else dealing with this exact problem with this tank! Thanks for the write up!
I did the same thing except for cutting holes. I just removed the back cover and set the fans angled in the back. The inkbird has been a great addition. Are you running the single light setup or did you add the second light?
 
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Lsuhunter

Lsuhunter

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I have 2 lights and the heat was manageable with the blues peaked at 75, but I slowly increased it to 100 and heat went up a degree or two. With summer coming, I knew I needed the fans because I think I want the 100 peak to last longer.
 

justy_

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I have the same tank (been running for a few weeks now) and have had heat fluctuations too. It would run in the 78-79 degree F range, bu throughout the day it would hop up to 80-81. That lid almost works too well lol. I wanted to avoid this, but I have been running the tank without the lid, and the temp is WAY more stable. The whole day it stays at about 78.5, which is great since it gets 100+ degrees where I'm at. But thanks for this thread! I might have to look into a DIY option like that. I would love to not have to deal with a ton of evap. all the time.
 
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SigmaVX

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I have a new flex 32 cycling and the heat is surprisingly high even without flow or pump running. Any updates on how the fans are holding up over time? Anything you would do differently today?
 
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Lsuhunter

Lsuhunter

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Everything has been stable for me, the fans are still working great. I did eventually add a small ATO and use about 1/2 gallon or so a week. I bought this small 2.5 gallon glass aquarium at Petco for $12 and made a lid to use as my ATO reservoir. It fit perfectly inside the piece of furniture I use for the tank.

At this point I am not sure there is anything different I would do, my tank is on cruise control at the moment. I like having and using the lid so this option has been great. If I ever went open top, it would only be to upgrade to better lights but have no intention of doing that. If you wanted an sps dominant tank, I think you would have too.
 

SigmaVX

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Thanks. I’m early on in the flex 32 journey and noticed a big creep in heat with the pump and power head running. Being down in FL it’s a bit harder to cool down. I think I’m going test out a fan - need something that can drop temp by about 3 degrees. really appreciate the post.
 
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Lsuhunter

Lsuhunter

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I am also in the south and it works surprisingly well. I figured the fans would be on a lot more than they are, they cool my tank down pretty fast before they kick off again.
 

SigmaVX

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I am also in the south and it works surprisingly well. I figured the fans would be on a lot more than they are, they cool my tank down pretty fast before they kick off again.
This may sound like a stupid Q but do you have the fans pushing air out of the tank or do you have them facing down to drive evaporative cooling? Purchased a new lid, 3" saw, and fans....so I'lll be giving it a try soon.
 
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SigmaVX

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Decided to give the DIY build a try as Lsuhunter mapped out. The upgrade went great and thought I would pass on a few additional things that may help or that may have changed.

1) the removed cages on the fans are excellent to use to mark your four holes for the screws. Find your center by making an X between the two opposing holes.

2) pick the place on the panel that is flattest. However there is a ridge on the underside of the lid that has to be notched to get screws in. I used a hack saw blade and needle nose pliers to take out a 1/3” section for each screw location. Use the blade to cut vertically in two spot that are about 1/3” apart and use the pliers to gently bend the 1/3” inch tab away.

3) the fans now come with rubber feet which I removed and had no issues. It is easier to take then off using a drill and pushing down on the rubber while unscrewing the screw.

4) hook fans up to an Apex control with the chiller setting

Bonus: I did these things but also swapped by AC Sicce pump for a DC Innovative Marine pump and moved my Apex controller further away from the tank as it runs hot (90 in some spots).

The culmination of these efforts and fan took the tank down to 78 in a room that runs AC at 77. Thanks again Lsuhunter.
 

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JReef3

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Great information everyone. Thanks Lsuhunter for posting your mod and SigmaVX for your version of it as well! I’m just starting to set up my Flex 32 and really appreciate all of these posts. I’ve read about the tight fitting hood being great for keeping evaporation to a minimum but having the down side of the tank running a bit warm. Love these DIY solutions! SigmaVX mentioned their room temperature is 77, I’m wondering what the temperature of everyone else’s rooms are that are experiencing heat issue with this tank.
 
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