Seeking advise on Fan to cooldown temperature

[Danieltwx]

A little bit information on my current tank.

 

3ft x 2.5ft x 2.5ft with 2.5ft x 2ft sump.

 

Keeping mostly soft corals, zoas, leathers, gsp and mushrooms.

 

Current temperature of my tank 30 degrees. Corals and fishes are doing well, however i would like to lower down the temperature by using fan.

 

I know that rodi top up will be a headache, however on a budget as chiller is out of budget at the moment.

 

Will like to seek some advises or recommendation of fan that can cool down my tank probably 2 to 3 degrees.

 

Will clip on fan do or those aquarium 5 or 6 head fans?

 

Any difference if i place the fan in the sump or clip on the Display tank?

 

Thanks!

 

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[ryanlio]

I think will be quite tough to get there.. but I'm following to learn more.. other then fan.. I probably will look at items that contributes to heat.. ie a DC return pump, led lights and wavemaker that has external motor (ie ecotechs).
PS. You got some Hardy corals there.. hehhe


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[soggycookies]

if you want to lower and maintain at 29 degrees i think fans still do a decent job for a tank of that size. wanting to go lower than 28 is definitely tough though, especially considering the lighting schedule warming the water.

 

also means your water would evaporate much quicker and in our climate you’ll prolly need your fan on most of the time if you’re looking to see and maintain a 2-3 degree drop in temp.

 

 

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[Danieltwx]

Oh yes equipment does contribute to the heat, thanks for the reminder.

Im currently running a maxspect r420r for 10hrs, 2 wave makers, 1 skimmer, 1 return pump & 1 external uv with pump.

Yes, planning for a softies tank

Hooked up an external thermostat yesterday, it was showing 31 degrees ytd afternoon and 30.3 degrees this morning. Suspect some problem with it, cant be only 0.7 degrees of cooling when the temperature is lower at night + light off.

Will get another external thermometer to veirfy.

Yup, i plan to maintain if possible at 28 degrees, using a thermostat to kick in the fan when the temperature increases! Probably running the fan the whole day

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[R0B]

Short answer... you would need 6-8 high powered computer fans running 24 hours to impact the water temp for a system of your size. However, a chiller is really your best bet.

Long answer (with a bit of science and math)... the specific heat coefficient of salt water is 3,992 per litre per degree. Your tank and sump is approximately 580litres. So to decrease your tank temperature by 2 degrees you would need 3992x580x2 = 4,631kJ of energy. Now a good chiller would have a coefficient of performance (COP) of about 4, whilst a large 50w 18 inch fan with evaporation effect has approximately a COP of 1.33 (or so I can deduce from the interweb) depending on blade angle and RPM and surface area covered. So let's assume you have this 18 inch fan you would need 4,631kj/1.33 = 3,488kj to decrease the temp of your water by 2 degrees. Now assuming, you are NOT adding any heat back into the water (so all lights, pumps, skimmers and no wavemakers are switched on) and given that 1 watt is 1j/second, you would need to run your 18 inch fan for 3,488,000/50w =69,776 seconds or 19.38hours to decrease the water temp by 2degrees. However, you will need to run lights, pumps and skimmers and wavemakers. Assuming this doubles the cooling requirements (which is probably an under estimate given ambient temp and your 30+ degree tank) you are going to need to run approximately a total of 30inches of fan blade across your DT and Sump for 24 hours to keep the water 2 degrees cooler. So depending on fan size that can be 6 (140mm) or 8 (120mm) high velocity computer fans running 24/7 (plus a rather large ATO and a dehumidifier).

The point is, fans are good for small systems to bring the temp down a little, they are cheap and effective. However for larger systems you need a chiller which is actually more cost effective in the long run.

Hope that helps

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[Danieltwx]

Yo Rob, thanks for the detailed explanations! Yeap, i probably will try a bigger fan or wait for a 2nd hand chiller to be chill down the tank!

Hopefully the fan solves the issue and i wont need to go for a chiller!

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[soggycookies]

agree with R0B, ultimately a chiller makes more sense if you want to maintain temp at 28 degrees and below. if it hits 31 degrees sometimes I really doubt it’d be able to lower the overally water temp to 28 before the fans go bust hahaha. not to mention your tank is also pretty tall so it might take an even longer time to bring the temperature down.

 

you could try going for a secondhand HS-66A hailea chiller. perfect for a tank of your volume imo.

 

cheers

 

 

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