How cold is too cold?

[toonces]

Hi all.
A quick bit of background:

I have a 60 cube set up in my garage here in central California. Electricity costs are crazy. With the winter upon us, it gets quite cold in the winter and it is very expensive to heat the tank.

Now that you know why I am pursuing this, here's the discussion.

Last winter I kept the tank at a low temp of 73 F. For about the last 6 months or so, though, I have cranked the thermostat on my heater all the way down to 68 F. The fish and corals don't seem to be adversely affected by this. So, I've been giving some thought to just what a low temp floor would be for these animals?

I think alot of that answer would depend on the animals, and where they are from. In my tank I have: live rock, snails and hermits from the Caribbean/gulf and Hawaii, two orange skunk clowns (captive bred), orchid dottyback (captive bred), 3 green chromis (unknown), a type of zoanthid and a type of button polyp rock (both unknown). Oh, and plenty of Aiptasia!

I know that the northern and southern limits of 'reef' locales would have cooler temps than the more equatorial areas, and deeper water species would be more tolerant of cooler temps. Additionally, inverts like zoanthids or button polyps that are more tidepool-ish would have a higher tolerance to extreme temps.

Then, there are reef animals that thrive in truly colder temps- for example the waters off of Tampa get down into the 50's in the winter. There are breeding colonies of volitans lionfish that live off the NC coast where it gets very cold- certainly well below reef temperatures.

I did some quick google searching and looked through some of my reference books, but I didn't find anything easily accessible about the low temperatures of mid-water reefs. I would expect it is around 20 C, but I could believe locally lower temps at the boundaries as low as 18 C maybe?

So, I'd like to open this up to discussion to see what boundaries of temperature tolerance have been explored. Last night I unplugged the heater to see how cold the tank would get and I'm hovering at 67 F, 20 C.

I look forward to your replies.
Toonces

 

[billsreef]

The places that see those low temp extremes for any period of time also don't have much coral growth, beyond a few struggling wayward colonies. Those breeding lions off of NC also happen to be offshore enough to be getting warm water from the gulf stream The Gulf Stream also happens to bring juvenille tropical fish to my temperate neck of the Atlantic during the summer and fall months, once the water drops below 68 they start dieing off. Personally I'd aim for 72 as a minimum for a tropical tank. If heating costs are too much, I'd move inside

 

[toonces]

Hi Bill.

Thanks for the input. I didn't realize those lions were offshore in the Gulf Stream. Makes sense though, I didn't think lions could tolerate the 'mild' winter temps of NC.

I used to collect tropicals in Shark River Inlet every fall when I was much younger. I understand what you mean about them all dying off in the winter.

I'm not really interested in starting a new way of life for reefkeeping. It would seem that it would be better to push the upper thermal limit to maximize growth rate. That's not my intent though. Unfortunately, I bought and set up this tank before I realized the astronomical electric costs in the winter here in Monterey. I agree that 72 is a much more sensible lower limit for a tropical tank, but I'm still curious where the lower limit lies. It would, of course, be species dependent, but I know that there have to be cooler waters associated with reefs in the more fringing north and south limits of where we get our tropical fish and corals from. I just don't know what that temp is. The only 'tropical' region I have any SCUBA experience with is Ft. Lauderdale, and that wasn't for very long. But I know that water had to get into the 60's in the winter, even if it wasn't for very long.

Moving the fish indoors isn't an option. I'll have to get rid of them instead. Before I do that, though, I'd like to discuss this low temp limit thing. At a minimum, it has to be more interesting than another, "Can I keep a flame angel in my reef?" thead.

 

[toonces]

I just browsed on the NOAA website a bit. I'm still trying to figure out precisely what I'm looking at, but under the link for coastal water temperatures, Key West has a January temp of 69 F, and Hilo, HI has a March temp of 71 F.

I'd be curious to see where Orange Skunk Clowns, Green Chromis, and Orchid Dottybacks are typically collected (although my clowns and dottyback are captive raised...) and then zero in on the low temp experienced there. Also, I'd need some sort of 'at depth' reading, since surface temps are probably warmer than temps at depth.

The NOAA temps above are at the surface. I wonder how much colder it is at depth in, say, Hilo or Key West?

 

[greenbean36191]

For the first 90-120 feet you're looking at an average drop of between 0.5 and 3.5 degrees from surface temps.

For reefs in the northern Bahamas and Florida the average winter temps are in the upper 60s. In parts of the Red Sea and southern Australia some reefs get down to the mid 60s. Like Bill mentioned though, most of those places are marginal in terms of diversity and health.

There hasn't been a whole lot of work done on low temperature stress in reef animals, so I don't think anyone has a really solid grasp on lower limits, but according to Ove Hoegh-Guldberg it's somewhere around 66. Of course that varies from species to species and based on acclimation. The temp of the original collection locality probably doesn't play very heavily into the equation unless you're adding new livestock.

 

[billsreef]

I think a lot can be determined from looking at the distribution and temperatures of given areas. Just from my own experiences and travels I would put 68 as a bare minimum limit, but not an ideal one. Try insulating the tank with some foam insulation wrapped around the sides to minimize heat loss, should make make keeping a better temperature easier and cheaper. I quite understand the electric bill thing, Long Island still has you Cali folk beat for high rates

 

[fish-freek-3000]

i kinda had a bad cool experience. i had a rbta that is normally in 80 degrees. my chiller got stuck on and the tank got down to 67. the anenome turned HOT pink. like it is really cool. i am gonna buy anotehr and try it again see what happens

 

[greenbean36191]

It sounds like the anemone bleached, which is what you would expect to happen with a change like that. It's not something I would try to induce.

 

[pledosophy]

Depends on the stock. I keep some of my tanks with the heater set at 69F all year, it is better for what is in that system.

Really depends on what you want to keep. I keep none of the fish you listed so am of little help.

For my lower temp, although tropical tanks, 65F is the lowest I would and have gone, with no repurcusions.

 

[ouuduy]

hey

hey

hey i have my tank set at 70 and have the same problem with electricity cost like you Everything seems to be doing fine as well.

 

[BeanAnimal]

Running on the ragged edge also leaves no room for problems. If you have a 40 degree garage and a 65 degree tank, a power outage will certainly takes its toll rather quickly.

As mentioned, adding insulatiuon to the sides of the tank will certainly help lower the heating costs. Covering the tank will also keep evaporation to a minimum. The dry air in the winter will tend to speed evaporation and at ~9000 BTU per gallon, you need to slow it down.