May 2003 - Unheated tanks

May 2003 - Unheated tanks

Goldfish, sticklebacks, white clouds. Say "unheated tanks" and that's what usually springs to mind, after all these aren't called "tropical" fish for nothing, right? Welllll, sorta, maybe, um, not always. The answer is "depends".

Certainly fish from equatorial Africa must be "tropical" and require high temperatures? After all, it Toronto and New York and unbearably warm in June (and sometimes May) then Africa has to ba a right scorcher being on the equator and all. But life ain't that simple, in other words "depends".

What does "unheated tank" mean exactly? Obviously it means sans one of those glass test tube type aquarium heaters, that much is certain, so, the temperature of the water will be in relation to the ambient temperature of the room the tank is in - and this is very variable.

I was born in the UK and now live in Canada. Neither of these are by any stretch of the imagination "warm" places in winter, and while my family left the UK in 1964 before the great technological innovation known as "central heating" became terribly prevalent, an unheated tank in England or Canada is not going to be as temperate as one in, say India or Singapore. "Unheated tank" in Singapore might be just fine for breeding discus or bettas which are notorious for requiring 80+ F degree tanks just to be happy.

So really it all depends on what your ambient room temperature is. I can remember in my youth, our neighbor when we first moved to Canada had their house thermostat set at 84; growing up in the perpetually rainy damp and cold British Isles, this house and indeed every store we went into in the winter was utterly and unbearably just too hot.

That was then, this is now, and in a post oil-crisis works, the halcyon days of hothouse thermostats is well and truly behind us; you're more likely to see a thermostat set at 54 in Northern North America than 84 - but note this is Northern North America; Atlanta, Dallas, Los Angeles are going to be an entirly different kettle of fish than say, Fargo, Cold Lake Alberta or any other place where polar bears would right at home.

Therefore "unheated tank" is really only meaningful if it's in an "unheated room", and I don't know about you but I've never lived in an "unheated room".

At this months editorial meeting in the luxurious marble floored, wood finished, red carpeted TFH editorial offices something of a spirited discussion erupted when our beloved editor told us the issue theme for this month was "unheated tanks". "What's the big deal about that" I said "I haven't used a heater since 1975". Jaws, in some, dropped in a way that looked like somebody beamed a dead rat into their mouths while others shrugged their shoulder and said "yeah, so"?

I've never kept discus, and while my fish interests tend strongly towards killifish which are for the most part cold-loving (more on this later) I've probably kept, at one point or another, every fish you'll ever find in a store and a few you seldom if ever see in stores. All in unheated tanks.

Two factors are at play here, room temperature and location. If your tank is near a big window and your thermostat is at 54 you might need a heater just to keep goldfish (the prototypical "coldwater fish") alive, but I posit this is an extreme case and I'm gonna go out on a limb here and suggest that most people have rooms that are closer to 72 than 54; given a (roughly) 5 degree difference between ambient room temperature and water temperature than that translates into a maybe 68 degreen tank. Have a look at your favorite couple of aquarium books and not the minimum temperature for the temperature range given for various species. I have a copy of the Innes book here on my desk and it's rather illuminating how many fish are listed with a temperature range where the first digit of the minimum temperature starts with a "6" and not a "7".

Not only do I not own a heater (and haven't for 25 years) but I haven't owned an aquarium thermometer for that long either. Does this mean heat is a problem for me? It use is, in the summer the tanks get too warm, but I've never seen a problem of them being too cold; I haven't even seen the white spot disease "ick" so often associated with cold water in my tanks for at least a decade if not longer.

Another factor to consider is, there's more than one type of aquarist and one type of setup. While I understand there are people with just one aquarium, I don't know any of these people personally - although I suspect a new neighbor of ours might be like this as I noticed last night driving past their house what appeared to be one large aquaria visible through their front window that I hadn't noticed before - but other than that almost without exception everybody I know that keeps fish has them in a battery of tanks in a fishroom. One heater per tank would make zero sense here in 30 - 300 tank setups; the mess of cords alone would be virtually unmanagable and in rooms like that either the central heat ducting it set to provide a little more heat or an auxilliary space heater is used - the oil filled (not fired!) ones really impress me: heat the room not the tanks!

Back to Africa: so what was I eluding to earlier when I said fished from Africa my not be used to warm water? Well, it all depends on the Terra Typica, or natural habitat of the fish, and what you'll find is that fish from the basement of the rainforest in equatorial west Africa do not do well are "normal" tropical fish temperatures. The floor of the rainforest is so choked out with overhead vegetation that the water below ia quite often dark, and surprisingly cool, as in 65 degrees F. My good friend Sandy Binder in Seal Beach California keeps his killies in an unheated garage and in winter, even in this suburb of Las Angeles, the water can get down into the low 50's and there have been no fish so far that suffer at this range. In fact one of the important observations during the 1980s when a raft of new killies became available was the fact that fish from the basement complex would not do well at the normal 72-76 range killies were usually kept at, no they wanted it to be 65 and DARK before they'd look decent and reproduce. Granted this is not the general case and is limited to some fairly rare, expensive and exotic killies such as bochleri, herzogi and joergensheeli - but these are true "cold water killies"; most others are happy as long as the water is under 80. Having said that, the South American annuals poke great huge holes in this, as some require it downright warm for killifish, while others, notably bellottii (pardon me for not keeping track of what genus they've put this poor pearlfish in this week) have been known to exist under the ice in outdoor ponds.

Thus endeth my rant! If the room your fishtank(s) is(are) in is warm enough for you to hang out in without a sweater, and unless you're keeping discuss or any of the very small number of true warm water fish, then I assert you can throw year heater away.

If your fish all die, then keep in mind I didn't really write this column, it was written by my evil twin who has been getting me into trouble for decades now.

I can't actually find a lot of information on this "unheated tanks are normal" debate which tells me it either goes without saying, or is just too heretic to make it into print, but here's a snippet from the Aquatic Plants Digest ("APD") that focuses on this particular debate.

This is your classic "coldwater aquarium" article that describes the prototypical coldwater tank with the classic "coldwater fish". What's a bit surprising here is that many barbs do fine are (much) cooler temperatures.

If we look at "classic coldwater fish" NANFA springs to mind. NANFA is the North American Native Fish Association and a quick look at their homepage shows a variety of attractively colors fish that you might not guess on first glance to be from North America. They actually have color! Ok, so the bluegill sunfish on that page will probably be more familiar to sport fisherermen than aquarists and looks more like a big cichlid, but most of the North American natives are generally smaller than that.

Here's a checklist of fish found in Florida waters, and it reads like a "who's who" of North American fish commonly held in captivity. The fish referred here as "topminnows" are in fact killifish and to confuse things, one "killifish" listed here is a livebearers, not a killi. This is why, boys and girls, we use Latin (scientific) names, not common names. I can't say there's a dearth of information here about these fish, but it does give you a very good idea about what's in the water there. Any of the smaller fish make fine aquarium inhabitants... sometimes unwittingly so. One in particular, the bluefin killi (Lucania goodei) sometimes mysteriously shows up in planted aquaria seemingly out of thin air. The reason for this is plants grown or held in Florida are used as a spawning media by these fish (that probably aren't supposed to be there) and since killi eggs are so tough, have a 2 week incubation period and can withstand being kept "moist" and not "wet" then they occasionally show up in pet shops plant tanks or even in peoples aquariums. They're charming little fish, tan with a black horizontal stripe, a blue dorsal and red splotch at the base of the tail - the males, anyway the females are in typical killi fashion, pretty much colorless. A hardier fish would be difficult to find.

It's not difficult to find the blackbanded sunfish (Enneacanthus chaetodon) in aquarium literature going back decades; what's disturbing is this site that lists them as endangered in Virginia, and illegal in the trade. However the banded sunfish (Enneacanthus obesus) is not in as much trouble and is even more striking that E. chaetodon, somewhat resembling a Rift Lake Cichlid.

Here is E. obesus again and from this page we learn it's range is from Florida to Rhode Island and that it's the smallest fish in this family and quite possibly the most colorful. There's another picture, taken by John Brill at It appears that the status of this fish varies, as does E. chaetodon, from state to state. In some states they're considered endangered, while in others they're not. This whole thing gets messy and the fines being as large as they are, you'd really need to investigate this quite thoroughly to see if collection or captive holding of this species is legal where you are... and that may not be easy. See if you can parse this gibberish: The good news is it's not a CITEs species; you can read all about CITES at