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overheating nano cube


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I would like to get some opinions on how to deal with a overheating nano cube DX. The problem is my ambient temperature, sits at 75-76 degrees. I cannot change this. The second problem is that the nano cube jbj stock pump puts out almost 3 degress by itself.


I bought a customized nano cube from Nanocustoms.com with a gorgeous 92watt +13watt sump in the hood. Its the coolest running integrated system I've seen, and this I won't change. Here is my temps:


Ambient temperature = 75.5 - 76


Tank with all lights on = 79.5


Tank with all lights & Rio90 powerhead on = 80.7 - 80.9


Tank with all lights, stock pump & Rio90 on = 83.5 - 83.9


So I'm just running too hot with this equipment, and need to change something or multiple somethings on my setup. Chris at nanocustoms.com is helping me, talking to JBJ on my behalf to address the heat generating from their stock pump.


I have a maxijet 606 on order to replace that stock pump, it should arrive tomorrow. I'll see how much heat it generates tomorrow. But with just this pump alone (adding on rios will raise the total temp too much), do I have enough water circulation to handle a good sized bioload of SPS's?


I could copy Chris's (nanocustoms.com) lead and go with a Tunze pump, which runs cool and would be plenty strong enough to split the flow, possibly install a rotating piece to distribute flow (would have to place this in the main show tank though). That might lower me to 80-81 degrees total during the day. Little high, but bearable I think. The Tunze pump runs $200 starting, that doesn't include the rotating part. That hurts a bit, but I'm dealing with this unexpected cost. It just has to be worth it.


Or, there are chillers. The iceprobe would be a decent solution, but there is no room to install it unless I drill a hole into the glass tank (on the back). I've only heard of one person (Bronco on this board) do this successfully. I'm told it compromises the integrity of the tank. So the other chiller option is a full size one, which can't be hidden in the cabinet, it requires open space to operate. That ruins the point of a nano cube.


I have no room for additional fans, and I can't adequately deal with massive evap issues those cause.


So, I'm looking for advice, suggestions as I wait to hear from Chris as to what, if anything, JBJ suggests. Either option above will cost me, so I don't want to have failure with what I try - and then have to pay again to go with another option.


Thank you,


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Hi Toni,


Ive been talking with JBJ and what we are going to do is try to Isolate the problem.


There have been modded/non modded customers who have had issues with the Stock JBJ pump.


Teh best way to gather this data is to have you go to:




and post your pertinent info to the "JBJ Nanocube Pumps Run Hot" section.





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Done! I've posted the details there, hope its specific enough. I received the maxijet 606 early, and have already replaced the stock pump with it. I'll test the water temperature in a few hours, and post that info there as well.


Thanks Chris!



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New info - several hours after replacing the stock pump with the minijet -


Temperature = 78.8 - 78.9, running all lights & maxijet 606 only, ambient temperature 73 degrees.


A definite improvement, but still rather warm, considering the ambient temp is down a few degrees from my last temperature measurements.

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Hi toni


Ambient is important, but your tank wont stabilize at ambient immediately (despite the fact ambient is down to 73).


Looks like we are doing good tho. Lets see what happens overnight as the temps equilibrate back down to 73 ambient.



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  • 2 weeks later...
Micro-Reefs Aquariums



Overheating has been a big concern for me with my cube as well. Because the air between the splashguard and surface stays stagnant it transfers the heat into the cube and if you have extra pumps, your temps stay even higher.


If you leave your hood open during the day, you will stay within ambient temperature of your home. It's when you close the hood that the heat stays trapped and rises. Try it and you'll see what I mean. The problem with leaving the hood open, is a lot of evaporation and oh course the look of an open hood in your home.


The only solution is a chiller, oh which I'm working on a prototype myself. It should be done by the end of this month early april. It will incorporate a small sump that can be hidden away from view as well as inlet tubbing that will enter through the back of the cube in chamber #1.


I'm in the process of reviewing the performance on some chillers that will be quiet and efficient for our cubes.


Hope this sheds some light.



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change out the rio as well and you should be set. the maxis put out much less heat than the stock pump and rio. just remember that many reefs in the world get over 83-85 degrees. i constantly run my tank around 80 and have found no ill effects. many reefers have said up to 83-84 there will be no problems. (im not brave enough to go that high as there is really no point)

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Or you could try the "doriftu's" idea of the cassette skimmer. this allows lower sump water height (adjustable) and if you put your powerhead at the top of the sump (like i did) (see pics i posted in "cheap nanocube skimmer solution" in do it yourself forum) the power head is almost completley out of the water and not an issue with water temps. i used a hagen 301 powerhead that has an inlet tube for water. i just added a length of hose to pick up from the bottom of the sump.

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  • 2 weeks later...

instead of opening up the entire hood...just flip up the feed lid...the cross flow will bring down your temp within 30 min by 1-2 degrees.

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I contacted JBJ directly and they sent me a new stock pump.. I am currently running on a MAXIJET400..I will replace that with the new stock and use the MAXI for more flow. To keep temp down, I will put the maxi in the 3rd chamber also, but just intake in sump.. motor above water.. I will use some tubing to take to intake grate or just over the top in the middle. I also use a little ceramic elephant that is about a inch high. Depending on where I rest the feeding lid on it, determines how open the feeding lid is. Anyway it helps.

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I did a custom Larnie mod and I'm running at about 79.8 with the stock and a maxijet400.

If things get warmer this summer my LFS suggests drilling some holes in the hood on the back wall of the hood opening (backing on the heat shield). This will allow for evaporation which is the key to cool.


..or so they tell me and these guys haven't pushed me wrong yet.


Just so you know, I have a set of upgraded fans in waiting right now, if you don't mind the noise you can double, even triple the air flow.

For double look at thermaltake fan.

For triple look at a delta fan...they use these on servers.


Chris at nanocustoms has some great/quiet offerings also, check them out.

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I have a Rio 400 and an Eheim 600 in the display. My tank temprature is 79-80 all the time.


I have my rio all the way up and the eheim about 3/4 open.


Lots of flow.

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I hope your chiller mod setup ends up being easy enough for a non-diy'er, it sounds great.


We haven't had high temps here since I last posted, and I left out the heater while cycling. I'm nearing the end of my cycle now, and will be just using the maxijet and rio90 for awhile. I want to order a tunze pump, same as Larnie's to replace the rio90. But that will wait. Its been months since I started my nanocube, and just as I was finally, finally, finally ready to begin populating it with stunning corals - I smashed up my car. I'll be cursing for a long time to come.



I'm going to try flipping the feeder hood as the first line of resistance when the summer heat hits. I'll hope that and just adequate flow works until JBJ comes up with a chiller, Mike or anyone else with overheating issues.


dja, I'm still waiting to see the longer term success of using the cassette tape cover, to see if its really one of those 'must do' mods for nanocubes. And all the eager diy'ers can work out the bugs!


Thanks for all of your suggestions. I'll keep watching this issue closely, online and with my cube. I'll pass on anything I learn that works out!



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One thing to check is to see which way your fan is blowing. Mine was blowing out, so I turned them around to blow in, and it pulled the water temp. down between 3 & 4 degrees. Still a bit too hot, but better. I'm going to swap my pump out later today and see how far that will help drop it. I'm also planning to put some slightly higher powered fans in...

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shao-lin nano

I was thinking of pumping water from the 3rd compartment of the back into an enclosed resivor placed inside a mini fridge and outlet it back into the tank. Gonna try and find a minifridge for under $50 to try this with a rio800 or stronger...hope this works. If it does, then it beats spending hundreds on a chiller.

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Shao-lin, my tank is at my office. But I could keep a soda in a mini fridge/chiller, beats walking to the kitchen! Anyway, that sounds cool. Let me know if it works!


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