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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