Article on aquarium temps. Thoughts?

[Seisage]

Came across this article on SeriouslyFish about recommended temperatures for fish and I have conflicting thoughts on it.

They make a very good points regarding the potentially flawed methods and timing of water temperature measurements in the wild, as well as temperature variability in the wild and the inconsistency in recommended temp ranges found online. However, I’m always a bit skeptical of the argument that if the fish “looks fine” and breeds, then it must be happy.

As always, I would love actual scientific longevity or stress studies on a variety of species kept at a variety of temperatures, or otherwise in-depth ecological studies that take seasonal temperatures and fish behavior into account. But those are both intensive and costly endeavors.

What are your thoughts on the argument(s) posed in this article?

Whaddaya mean, too hot? — Seriously Fish

www.seriouslyfish.com

 

[Colin_T]

It's a good article. I have collected fish over the years and went back to the same spot at various times throughout the year. On the collecting sheets there was a spot for date and time as well as water chemistry and a description of the area, plants, organisms, etc. The water temperature various depending on the size of the water body, shape (pond, narrow creek, wide river), the depth that the thermometer was put, the time of day and the weather at the time, and location and flora (trees shading an area vs full sunlight).

I used to take water temperature from the surface and the bottom (assuming I could get to the bottom) of the waterway. Even on the same day at the same time, there was generally a noticeable difference in temperature between the surface and base of the waterway. In 2000 I was down in Walpole (south-west of Western Australia) and found a pond that had some salamanderfish (Lepidogalaxias salamandroides) in. There were young fish around the edge of the pond in 1 inch of water. The water temperature there was 32C. At the bottom of the pond (about 4 feet down) the water temperature was 12C and there were adult fish down there. Presumably the young stayed in the warmer water to grow faster and be closer to small flying insects, which they ate.

I have found similar results in numerous ponds or non-moving water bodies around the south-west of WA. And in moving water there is not normally a big temperature difference between surface water and the water near the substrate, but there is a noticeable difference in temperatures throughout the year. In summer the water can reach 32-34C and in some cases higher (up to 40C). In winter the same locations can be 5-10C.

I used to set my aquarium heaters to 18C and let the temperature come down naturally during autumn. In spring the temperature started to increase and by mid summer the water was regularly on 30C. I found a lot of the fish would colour up well in spring and breed right through spring and summer and stop breeding around mid to late autumn.

The cooler water is a must have for danios and barbs, which naturally occur in cooler water, and a lot of common livebearers do well with a cooling off period. In Perth (Western Australia) there are or were a number of people that keep "tropical fish" in outdoor ponds all year round. We had plenty of customers that had swordtails, platies, guppies, mollies, rosy barbs and even rainbowfish in ponds all year round. I did it myself with rainbowfish and developed coldwater strains of new Guinea rainbowfish. These fish could live in water that dropped down to 5C over winter and reached 40C+ in summer. The colours on them were incredible and comes down to a combination of sunlight (UV light), lots of insects in their diet, and to a small degree, the fluctuating temperatures. The temperature didn't go up and down rapidly during the day, but it did change over the course of a year and it's my opinion that fish and other animals need this variation.

Every person that lives on this planet enjoys certain times of the year better than other times. I like autumn and spring because it has long days and the weather isn't too hot. When it hits summer, people are fine for a month or so until it gets really hot. Then it becomes unbearable and everyone wants it to cool down. In winter the same is true but it's the cold weather people don't want. A couple of months of cold, icy or rain soaking weather is enough for most people to say enough, I want some sunshine and warmth. We need this variation to let us know the world is changing and so we don't go nuts from the weather. Three months of the same weather is the most people and animals can take when it's really hot and dry, or cold and wet.

Animals, birds and fish go through this same experience. The days start to get longer and the temperature increases a few degrees and birds start breeding. In autumn as the days shorten a lot of mammals breed and gestate during the cooler months, giving birth in late winter or early spring. There is more food available at this time of year due to winter rains encouraging grasses and insects that start the food chain.

In the tropics, subtropics and more hospitable areas of this planet, a lot of freshwater fishes breed when it starts raining. The sudden influx of cold/ cooler water can wash in food and expand the size of the waterbody, sometimes even flooding it into other areas. This massive influx of clean water washes out any pollutants that have built up during the dry season and provides clean water for the remaining fish.

In areas where the water freezes over, fish can either go dormant or slow right down during this cold period. In spring when the weather warms up, the fish come into breeding condition and start reproducing. For these fish, the sudden influx of freshwater occurs in spring when the snow and ice melts. Insects start breeding then too and the fish have lots of food and lots of clean water.

The first fish book I got had the temperature ranges for the fish listed in it and I was shocked because it showed various tetras and barbs (sold as tropical fishes at the pet shop) as needing cool water. More modern books have a much narrower temperature range and some simply have 24C or 26C as the "ideal" temperature for a tropical fish tank. Most pet shops say 24C is the recommended temperature for a tropical tank but they are offering a temperature where species from warmer water can live with species from cooler water. This isn't really the best way to go for the fish and zebra danios are a classic example. If they aren't kept in cool water most of the time, the females can develop eggs and become egg bound.

Having some temperature variation is beneficial to most freshwater fish and essential for some species to breed. Allowing the aquarium temperature to fluctuate a bit throughout the year can save money on heating costs and provide a more natural environment for the fish.

 

[GaryE]

I can't talk about my local waters as @Colin_T can, as right now in January, in normal weather, I would be able to walk on them. But in my entire fishroom, I have 3 heaters plugged in. That's for 60 tanks.
I have watched heater creep in the hobby, for years. I would say in many cases, suggested temperatures have climbed several degrees, for no reason I can see. Fish that thrived at 23 forty years ago are now said to need 26 or 27, in the unscientific, pet store side of things. My cynical side says it costs $50 for a good heater in a local store, and they no longer last for many years as they used to - they are disposable tech. If I ran a store and were trying to stay open, I would find temperature creep very easy to convince myself of. We all want what we want to be true.

Maybe there is no answer and we come to what anyone who reads me is probably sick of seeing. Every individual species has to be studied on its own, and if we care about keeping them in somewhat natural conditions, we should use words like "study". Conditions in one region will be similar. A pond operates one way, and a moving river another. Floodzones have their own dynamics.

A temperature difference of 2 degrees can be fatal for some specialized species from extreme habitats, and perfectly acceptable for others from habitats with changing seasons.

I overwinter my rainbows at 23, and breed them in summer at 26.

I choose my fish carefully. Many times, I have not bought a very interesting species because I knew it would need a heater.

We shouldn't be assuming fish will adapt to our wants. We really should adapt to theirs. How is a good question, because the info is hard to get. We have snapshots of certain times of year, and we have collecting reports. I largely agree with the author of the article cited, in general. Tanks can be kept very warm, which wastes energy and probably shortens fish lifespans. But I would never keep a Discus or a Dicrossus at 20c.

 

[Magnum Man]

could this temperature creep be a knee jerk reaction, particularly at the pet store / wholesaler level, to control Ich or similar, at the conditions the fish are kept in, at those locations???

 

[GaryE]

could this temperature creep be a knee jerk reaction, particularly at the pet store / wholesaler level, to control Ich or similar, at the conditions the fish are kept in, at those locations???

Ich will still do fine at 26. TB and most internal bacterial infections like it warmer. A lot of petstores don't practice what they preach - the tanks are often unheated. They advise you to get a heater, but they don't all do it themselves.

I think it's a trend - the way trends can grow with no basis, kind of like fashions. No one knows how this one got started, but I see a lot of online sources pushing it. In the era of books, it wasn't a thing, but since we've leaned into a no editor world, people offering info can be kind of careless. It seems to climb 1 to 2 degrees celsius per decade - a kind of global tank warming.

Temperature is also not easy if you want a simple fishtank world, either. Yesterday, a visitor looked at my Parananochromis brevirostris, a Gabonese dwarf Cichlid that lives a short life above 24c in tanks, and a long one at 22. He said "Wow. The colours are really different, but shapewise, it could almost be a kribensis." It was an observation I'd agree with, but it could be a trap, too. To get an even sex ration with kribs, 26 is a good temperature. And there's only 750 or so km from P pulcher (kribs) to my fish. But over that distance, things change. Geology. Elevations. Forest cover remaining. They all matter.

We have this thing about over generalizing. It runs deep, and most of the time, in everything, it leads us astray. I can see how it would be a problem in the US, because all those Americans are exactly the same. Yeah. Over generalization. We love doing that.

Sometimes in the next 2 months, someone will come here and sincerely post something like "Cichlids love to be crowded and to live at 25 in hard water". It's almost guaranteed.

 

[Seisage]

@GaryE You make a very good point regarding the industry side of the hobby. It’s always important to remember that as much as we want to hobby to be informed by real science, it is ultimately the industry’s ballgame. Fish stores and aquarium suppliers are the ultimately the most common disseminators of information, especially to those who trust easily and don’t do much research themselves.

Honestly, I’d hazard a guess that your cynical side is at least partly correct. Even without having the point of reference of the hobby as it was in the 20th century, I can tell that things are increasingly becoming ruled by gadgets. Tech has become a major factor in the hobby, to the point where I know there are plenty of people who get into it simply for all the gadgets they can collect. I would not be surprised if heaters and the way they’re treated as essential for every tropical tank is just a part of that same trend.

If one were to don their tinfoil hat and extrapolate further, one might wonder if the temperature creep ultimately promotes fish sales by reducing lifespans. If this pattern exists, however, it most likely isn’t a purposeful effort by the industry and is rather a happy accident, the cause of which they may not even be aware of.

Then again, maybe the temperature creep is due to continually updated measurements in ever-warming habitats.

I did find this study on temperature tolerances of a couple south american tetras that’s pretty interesting. Essentially, they can adapt to higher temperatures, but only a few degrees higher than the average temps than their native habitats. That said, their ability to survive decently well at 30+ degrees is impressive.

https://www.sciencedirect.com/science/article/abs/pii/S0306456519303353#:~:text=In%20neon%20and%20black%20tetras,brain%20orexin%2C%20leptin%20or%20CART.

 

[anewbie]

A lot depends on the species; i'm keeping my wc discus at 84 right now (not sure if that is good) but read a lot of different article on temps et all with some folks claiming 82 and even 78 is fine; what i can say is when i do a water change and the temp drops to 82 they immediately run to the other side of the tank to be by the heater until it warms back up - so they definitely prefer 84 to 82 - i've had rams die because the temp drops a few degree (bloat up); other fishes are more robust and some species actually depend on deep shift of water temp over time to trigger certain behavior like breeding and i think i read somewhere that digestive issues can occur if the temp doesn't change for some species. I don't think there is a right answer and i definitely thinik 'breeding' is not an indication of a healthy fish but again it depends on the species.

 

[GaryE]

@anewbie Your examples are great, because both rams and discus are heat lovers, and need warmth. Neither would be appropriate fish for someone with my set up to keep. Rams come from a savannah where the sun easily gets to the water.

Amazon fish are often trapped as side rivers dry up and sand bars become land. The fish become concentrated in ever shrinking pools, and live in a kind of suspended state. It strikes me as the hot version of what my local Canadian fish live like in winter. I can't help but think a lot of our tanks replicate those miserable, just trying to stay alive states, except the blessed floods never come.

Every Cory breeder knows you stimulate egg laying with a rush of cool water, to simulate those life saving/changing rains.

 

[GaryE]

Somewhere in the cabinet I keep old gear in I may still have one of my stainless steel, clip on mercury aquarium thermometers. The brand I had showed a different coloured safe zone for temperature, from 72 to 78 fahrenheit. I guess if I still have it, it's archaeological evidence of 1970s aquarium practices. I see so many postings saying newcomers were told to start at 80, or 82f. I don't think there's any conspiracy involved - people put heaters in and they often have tanks at those temps, once lights, etc do their work. So it becomes normal (in aquariums) and we all suggest our own versions of normal.

In my fishroom, admittedly not a typical set up, I have 2 linear piston airpumps that produce air warm enough that the pipes carrying it feel warm. I just measured it, and it enters the system at 42c. It runs through a loop of 50 feet of pipes to valves and then to airlines, and loses heat as it goes, but at its farthest points, it is still hitting the water at 24c. I have led lights that while energy efficient, throw heat. Right now, my room temperature (measured on 3 different gauges) is 23.2, but my water temperature is 24. At night when the lights are off, the room temp drops to 20-21, but the water stays steady. I'd like the room to get to 19c at the lower levels, but even with the heat turned off in winter, it stays above 20 with the dehumidifier, lights and pump.

If I even have a point, it's that we add heat beyond our heaters, and that also influences how we do things.

Heaters tend to stick too. Even the expensive ones do. Most of the ones I have in my heater box/bin have tape on the cords, showing where they stick. You can set them for whatever you like, but most go too high at 27, 28... They are not the best tech unless you buy expensive gear to supplement them.

Maybe we just look at our tanks, look at the temps, see that nothing looks dead and say we must have it right as a result? From that, we give advice, rather than from looking up capture info on habitats.

 

[anewbie]

Heaters tend to stick too. Even the expensive ones do. Most of the ones I have in my heater box/bin have tape on the cords, showing where they stick. You can set them for whatever you like, but most go too high at 27, 28... They are not the best tech unless you buy expensive gear to supplement them.

Well the expensive gear is not that expensive; you want something like inkbird or similar; esp since the pandemic heaters have gotten miserable both with failure rate and sticking. On my critical aquariums i have alarms with alerts if temp goes too high or too low. Yea it cost a bit but not as much as the fishes in those aquariums.

Anyway I think the thread point is that for many species we keep the fishes too warm and that is probably true - after all how many folks keep panda cory at 78 or 82 but the reverse is true; my 172a died because i kept it at 78 instead of 84 (not a whole lot of info on this species); now to the article point not a lot of people have 172a and certainly nearly every chain store has some species of cory - some prefering 72, 74 or 76 depending on species but a lot of them will be thrown in aquariums at 78 or higher.

One thing the article fails to mention are domestic species which probably have - through selective breeding (intentional or unintentional) been adapted to a different temp than their native habitat.

 

[GaryE]

One thing the article fails to mention are domestic species which probably have - through selective breeding (intentional or unintentional) been adapted to a different temp than their native habitat.

I'm not convinced of that. There are linebred mutations that hobby lore says need warmer water. They are more fragile than wild types. But even that - we would need a linebreedigng expert like @emeraldking to confirm.

Fish are mass produced in warm countries, and some have been captive bred for 50 years or more. Maybe they've adapted. I don't see why they would, as that's a short time in the life of a species, and farms don't want "units' dying. I think it's not mentioned in the article because it isn't a factor. It's pretty clear that very few hobbyists breed their fish, so there is no selectionfor home aquarium conditions there. The fish are "manufactured" on the farms for consumption, in most cases, and they make it young adult size in outdoor ponds or room temperature (in warm places) stock tanks.

I think there's a comforting myth that fish adapt to our tanks. If we get serious, we should adapt our tanks to them. If we don't, they'll still survive, but maybe not for as long.

 

[anewbie]

I'm not convinced of that. There are linebred mutations that hobby lore says need warmer water. They are more fragile than wild types. But even that - we would need a linebreedigng expert like @emeraldking to confirm.

Fish are mass produced in warm countries, and some have been captive bred for 50 years or more. Maybe they've adapted. I don't see why they would, as that's a short time in the life of a species, and farms don't want "units' dying. I think it's not mentioned in the article because it isn't a factor. It's pretty clear that very few hobbyists breed their fish, so there is no selectionfor home aquarium conditions there. The fish are "manufactured" on the farms for consumption, in most cases, and they make it young adult size in outdoor ponds or room temperature (in warm places) stock tanks.

I think there's a comforting myth that fish adapt to our tanks. If we get serious, we should adapt our tanks to them. If we don't, they'll still survive, but maybe not for as long.

I would say they adapted in the sense that the ones who could not handle the heat passed away or passed away sooner hence were less likely to be used for breeding of future fishes. I don't think this article even considered captive bred fishes - esp those bred in large warm farms. There is of course negatives to these farms as many of the fishes are heavily inbred or by breeding them to produce specific traits (such as unnatural colouring); they have other negatives. Of course it isn't a given that a pretty fish has negative but my personal experience has been they are less hearty for one reason or another. There are of course other negatives - such as in most dwarf cichild the ability to signal violence via colour change is often lost... this is of course a divergent but i'm pretty sure the author could care less about genetic change due to farm breeding of fishes.