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a rabid squid

Oct 6, 2004
im really contemplating getting a nautilus. i just want to know what every one thinks. im a pretty good aquarist and have the money for a like 300 gallon tank ( a poly tub) and was wondering if anyone has kept one relatively sucsessfully.
If you search on Nautilus, you'll find several discussions of this very idea - keeping a nautilus. Most people who consider it eventually abandon the idea - it requires a chiller as well as a very large tank and has its difficulties.

Are you prepared to chill that size tank? That would be a hefty chiller, perhaps an old aircon unit diy would be the best option. You'd still need some titanium piping.
I dont know how much a real chiller would cost that could do that sized tank.

Also a Calcium reactor is a good idea.

Maybe give everyone an idea of the entire setup. 300G sounds a pretty good size, but make sure the tank is as tall as possible.
I am also considering a naut, and from what I've read, height is as important as chilling capacity. I also agree with Feelers about the calcium reactor. Another thing I've noticed is that the initial expense (unless you already have the equipment) can be prohibitive. I have pretty much set my sights on next year, after the tax season.
Feelers said:
Are you prepared to chill that size tank? That would be a hefty chiller, perhaps an old aircon unit diy would be the best option. You'd still need some titanium piping.
I dont know how much a real chiller would cost that could do that sized tank.

An air conditioner big enough to chill it would probably be more expensive than an appropriate chiller (People have done DIY chillers out of window air conditioners, but I don't think that would cut it for a huge tank like this--I think you'd need to use a central air system!).

You might try a smaller, but still tall tank. Don't they make a 120 that's relatively tall? You might try a couple of "bong coolers" in conjunction with an auto-topoff if you didn't want to buy a chiller.

Hi A.R.S.,

Chilling a large tank to 'cold' temps (45 to 55F) doesn't have to be a deal breaker but it does require advance planning.

For a Nautilus you should have two things working in your favor:
1. Lighting - You don't need much since the Nautilus lives pretty much in the dark. It's not like doing a reef with a bazillion watts of light dumping huge amounts of heat into the tank.*
2. Water movement - Again, you don't need much so you won't need to have a bunch of powerheads dumping heat into the system either. [It's my understanding that these are open water animals that don't encounter the high currents associated with near-shore habitat.]

The main thing you need to do is insulate as much as possible. If you're going to use a 300 gallon tub, consider building a box around it and filling the resulting void with expandable foam (sometimes referred to as "pour foam".

OTOH: With a modicum of woodworking skill you could build a modified GARF style plywood tank and use that blue or pink styrofoam board that contractors use in house construction. That plus an acrylic veiwing window will give you a tank that's thermally efficient and that allows you to veiw your Nautilus from the side (a more aesthetic viewing angle IMHO).

On the subject of converting a window air-conditioner, I suggest you root around on the Reef Central site. There have been several threads on this sort of thing and the consensus among the folks who have done it is that the conversions work very well. It's also apparent from the same threads that, although the conversion isn't extremely difficult, the best results are obtained if you or a close friend happen to be an A/C repair technician.

*A member of our Cold Water Fish mailing list recently converted two of his tanks from tropical reefs to cold water and says that his chiller is running significantly LESS under the new regime. He attributes this to the lower light levels he's now using.

Coolly yours,

How much are "real" aquarium chillers that can do that size tank? I'm looking at a 1/2hp chiller that can do 120 gallons about with a temp difference of 15 C, and thats about $600 USD, and from what I have seen of american chiller sites thats quite cheap - most 1/2 are around $1000 US I think?

When you get to that price range I would imagine an old aircon unit might be cheaper - and they are really good too. A huge cooling capacity. Its just annoying because you need to buy the piping.

Just found this http://www.northcoastmarines.com/chillers.htm , theres a good sized one there!!!
First, a temp differential of 15 degrees C is a lot. That would make a tank around 45 degrees F, which is downright frigid, probably even for a nautilus! That same chiller would keep a 240 gallon tank at close to 60 degrees F, which is probably a bit more like it.

Second, you lose mucho efficiency converting an air conditioner. The coils in an AC aren't titanium and you don't want to tear them out and replace them with titanium (~$100 I think) unless you know how to deal with freon (well, the modern equivalent, anyway, hence Alex's comment about knowing an HVAC). That means you have to paint the coils with epoxy or some other insulator to protect the coils and your tank from corrosion (and yes, that paint will crack after a while).

If you're talking about cooling 300 gallons of water even 5 or 10 degrees C, a little window AC isn't going to cut it, you're talking about a multi-thousand dollar central air system. I seriously doubt you could find one of these used because 1) they cost so much people use them until they die and 2) I believe the HVAC that takes the old one is liable if the chemical is released and isn't going to be very eager to give it away.

Those are my rational for not recommending an AC chiller. Every article about them I've read concludes that they did it for the experimental enjoyment, and they're going to buy their next chiller :smile:

Well here you can get an old air con unit - not a window - but a full free standing one for about $1000 nz or less.

I have absolutely no idea of the Fahrenheit scale :biggrin2: - for my tank I'm looking at about an operating temp of 10-12C which is pretty cold.
I dont know what the normal room temp would be either?

I have seen people in NZ who have used old air con units and they were happy with them, but I'm geussing that they are cheaper here than in the US. And from what your saying much more available.?
I was talking about one silimar in size to this:

Its pretty massive, but it wouldnt be on much. Sorry about the stupid photo haha.

Apparantly you loose the coolant, and just have it refilled by the aircon people, and they can make it all air tight ect after getting the Ti coils.

I have read that most people are very unhappy with beer fridge chillers ect(for obvious reasons :biggrin2:) , but I havent found many that wern't happy with the aircon converted ones.

I have considered it, it gets me thinking....

Trade Me
I know nothing of air con, could you use something like this? Or too little?
The one in the photo is pretty small, not much bigger than a room A/C. When I say central air I mean one the size of a washing machine. Really we'd have to do the energy balance to see how many joules we're talking.

Sorry about the Fahrenheit--being an American I think in it :smile: 12 degrees C will be much closer to the 60F than the 45F.

I'm not saying that an ac conversion won't work, its just we're required to scale the concept up quite a bit for this application. At that scale I believe the inefficiencies inherent to the conversion (which are acceptable at the small scale that most people are doing) will end up costing enough extra energy per month as to make the initial cost of a more efficient machine (designed for the application) worthwhile.

I havent read anything about the power consumption of a diy chiller, I might have a look into it - because as you say it might be huge!!!

I was thinking about making my own as I wouldnt be able to afford another (larger) chiller if I upgrade my tank.
Air conditioners and refrigerators are very inefficient. If you have a heater, you have an electric resistor or a combustor that's turning electrical or chemical potential energy directly into heat. You can't just "make cold" the same way, you can only "move" heat elsewhere. A heat pump takes a substance and compresses it, which causes it to heat up. Then you take this and cool it down to room temperature in a radiator (move the heat away). Then when you decompress the material it will be cooler than room temperature. This is obviously a very ineffcient way to do things. If the machine were 100% efficient, the same amount of heat and "cold" would be generated. If you put a fridge in a room, opened the door and turned on a perfect machine, there would be no temp change in the room. In real life where this is very inefficient (I would guess less than 20% efficiency? If you think that's too little, your car engine runs at about 30%!) most of the energy that goes in is lost to heat and very little "cold" is generated. Put the fridge in a room and the room heats up (why half the air conditioner needs to be outside for it to work!)

Here's how to look at it in a reef: People complain about the power consumption of their metal halides. No one chills their tank to the point that it completely cancels out the heat added by the halides. Why? Because it would cost a lot of dough. By my guess above it would cost 5 times as much.

This is why parents always get mad if you turn the air conditioner up real high--if you leave it running it can add hundreds of dollars a month to a power bill.

Cold tanks are expensive, but wow, some of the jellys and stuff you can keep are increddible. I have found chillers work quite well if the house is air conditioned, you sticky tape sheets of styrofoam to tank sides and back (for rectangle or bubble wrap for round) to insulate and don't use bright lights or water cooled impellors like those in most powerheads. My hood fans are quite strong and without the halides on actually cool the tank quite well but create a lot of evapouration.

I have yet to play with using chilled air filters but for a naut tank where current is unimportant it could very well be the go. Deeper tanks allow for some cool hidden air filters and the extra height would give chilled airbubbles more contact time with the water.

After all that I wish I could afford to have a big cold water tank at the moment. But temps are getting near 40 deg C during the day so I'm happy keeping tanks below 28 degC!!!

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