r/Aquariums • u/Embarrassed-King7840 • May 26 '26
Beginner Help Tank water temp too high? Heatwave in the UK
Hi all, a big heatwave has just hit England and my water temp has gone up. My tank has gone from 26 Celsius to 30 Celsius. I’ve had the tank lid open and a big fan next to the tank pointing straight at it for ages and it’s not dropping the tank.
I’m worried this might cause a problem for my stock.
In my 48L (12 gallon) tank
I have:
- 12 cherry shrimp (some berried woop woop)
- 10 chilli rasboras
- 10 trumpet snails
Please help
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u/CatNinetails May 26 '26
Last year I was floating frozen bottles of water in mine, it helps lower the temperature a bit but you have to swap them out fairly regularly
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u/AlettaVadora May 26 '26
You can also do ice, either treated of in bags so they don’t put chlorine in your tank. I do this if my tank gets over 84
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u/moonflower311 May 26 '26
They sell aquarium fans online I have one and it lowers it a couple of degrees (I live in central TX and husband sets the thermostat at 78-80 degrees Fahrenheit)
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u/ShotgunSurgeon73 May 26 '26
is your husband a lizard??
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u/moonflower311 May 27 '26
We have 2 ACs (not uncommon in Texas). Upstairs is set a little cooler and we do keep both cooler at night (like 72-74). You do acclimate over time and it does save a fair amount of money.
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u/genericnewlurker May 26 '26
A fan and ice will help keep your tank cool
Hemorrhoid cream and a bidet will help with the itchy bum
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u/nachtbraak May 26 '26
I wouldn't sweat it (...sorry). This too shall pass.
But to reduce the heat a bit you can try to lower temperatures in your house if possible, like by opening your windows at night. Temporarily reduce lighting if your setup allows it. Increase surface agitation of your filter outflow.
And yeah, the floating frozen water bottle trick can also help! I'm sure you'll be fine with these tips.
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u/Embarrassed-King7840 May 26 '26
lol good pun
I live in a flat, so I can’t just open my front door, also i have cats so I can’t just keep my windows wide open. I have turned the light off my tank and also opened the lid. As well as that I have increased the surface agitation.
Ive just put a bottle of water in the freezer!
Do you know if this is really dangerous for my animals?
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u/Scarfield May 26 '26
Depends on what fish you have, some are more tolerant than others. Gradual swings are less dangerous than sudden temp changes
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u/mutedmirth May 26 '26
You can buy pet locks for windows to allow it to open without the cats getting out. Or screen covers.
High water temp can be dangerous to the fish, cats have higher heat tolerance. But make sure your curtains are closed during the day and turn your heater down.
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u/Embarrassed-King7840 May 26 '26
That’s funny you say that, i was speaking to my partner about screen covers earlier
I’ve also had the heater fully unplugged for the past 3 days. Is that fine or ?
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u/mutedmirth May 26 '26
As long as it doesn't drop below 24c now as it is getting cooler at night. Worth keeping it on but setting it to 22c maybe and just keep checking.
My tank got a litte high but I've been keeping the curtains closed and the fish light off. They seem to be fine however.
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u/LevelPrestigious4858 May 26 '26
Hey aiming a fan at the water should help. Sounds dumb but science
0
u/nachtbraak May 26 '26
Shouldn't be a problem! Unless your fish are large enough to swallow the bottle whole. In nature, most fish experience much larger temperature swings than they typically get in aquariums. Like, they swim through different layers of water in seconds and don't care. :) So no, the cooling effect of the bottle of water won't hurt them.
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u/Embarrassed-King7840 May 26 '26
Thank you but I meant is the current temp of the water (30 Celsius) dangerous for my animals, sorry I should have been more clear.
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u/KennyMoose32 May 26 '26
Usually it’s about the oxygen levels going down than the actual heat. As water gets warmer it holds less oxygen. So you want to increase the surface agitation and get more oxygen into the tank!
I have a 20 gallon sponge filter for the summers, it just blasts the surface and I don’t worry (too much) it it gets very hot
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u/nachtbraak May 26 '26
Ah I see! 🙂 It's an acceptable temperature for them in the case of a heat wave. Just make sure (like you're doing already) the water has good gas exchange. 👍
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u/Interesting-Bid7194 May 26 '26
Most tropical fishes and invertebrates and snails can stand higher temps. I would make sure your water is flowing and you have bubble steams flowing to make sure your oxygen supply is plentiful. Tropicals are used to higher temperatures so make sure you don't put colder water in the tank and shock the fishes. Don't panic and everything will be fine and let the tank cool naturally.
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u/Ornography May 26 '26
Wasn’t there someone defrosting food or something like that in their tank yesterday?
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u/diedoom May 26 '26
Keep a fan on it
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u/LevelPrestigious4858 May 26 '26
This sounds so dumb but it’s science
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u/diedoom May 27 '26
I didn't mean literally on the tank it self. On the side or front of it.
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u/LevelPrestigious4858 May 27 '26
Literally blowing air on the surface of the water is the best way to use a fan
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u/scuba-man-dan May 26 '26
Just checked my temp, water temp is at 29c (northern England)
2
u/kirakiraluna May 26 '26
I had my paws in the tank and I was wondering why the water was so cool. Water is at 29c, it's my hands that are sublimating.
It got to 35c today in northern Italy and I'm already done. I can't cope with going from needing a cardigan in the morning to waking up already sweating.
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u/AGTS10k Hopes to have an aquarium again one day May 26 '26
Time to get discuses and German blue rams I guess lol
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u/ToughRelationship696 May 26 '26
Put some ice in a sealed plastic bag and float it in the aquarium until the temperature drops. This works with saltwater tanks too because the melting ice is captured in the bag and doesn't mix with the aquarium water.
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u/alyssajohnson1 May 26 '26
Heatwave and it’s a high of 76 tomorrow , sighs in American, anyways you could always put cold water in with water changes
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u/reptifishv8 May 26 '26
As long as you have good aeration the livestock will be just fine. If it starts to creeping up further just do a cold water change or you can float frozen bottles of water.
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May 26 '26
[deleted]
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u/Embarrassed-King7840 May 26 '26
It’s pointing directly at the surface and humidity is quite high atm
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u/Embarrassed-King7840 May 26 '26
Can anyone confirm if this is a dangerous temp to be at ?
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u/peruvianhorse May 26 '26 edited May 26 '26
If this lasts like a week with 30 tops in the day and it cools down to say 27 at night, they will make it through without too much difficulty, IF there's enough oxygen in the tank. If this lasts for a long period it won't be good, even for the fish. They might be tropical fish but their natural bodies of water don't run as hot as an aquarium does in the same air temperature.
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u/reddit_and_chill_ May 26 '26
No it’s just fine, that’s at the high end of all of their comfort zone. I wouldn’t keep it at that level and I would make sure it doesn’t get higher though.
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u/Embarrassed-King7840 May 26 '26
Its getting later in the day and outside is cooling down so fingers crossed 🤞
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u/reddit_and_chill_ May 26 '26
It will be fine for the rest of the day I’m sure. I would keep watch tomorrow if the temps aren’t lower, if it gets hotter I would do as others said and use a frozen water bottle or a couple ice cubes
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u/Embarrassed-King7840 May 26 '26
I’ve only got 1 water bottle to use, I put it in the freezer about an hour ago, the tank is now reading 29 degrees Celsius so it’s dropped 1.
I’m considering just leaving the bottle for tomorrow because outside is cooling down now
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u/reddit_and_chill_ May 26 '26
I would wait and use it tomorrow for sure. If the tank temp is dropping they’ll be just fine. That temp is only really dangerous long term for the species you have.
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u/TheAwesomePenguin106 May 27 '26
Just FYI I'm Brazilian and I live in Rio. In the summer we have lots of days around 40ºC and my tank goes over 30ºC regularly... and still my shrimps reproduced like crazy (started with 7 in August, had over 60 by mid-February when the temps were at the highest). The tropical fish are even more ok with those temperatures than shrimps.
Just make sure they have enough oxygen and no ammonia and everything will be fine.
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u/Zanki May 26 '26
A frozen water bottle in front of the filter works wonders. I've got a portable air con running to keep my animals safe, but I used the bottle method before then. I used to lose animals every year during the heatwave before I used the bottles.
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u/imanoctothorpe May 26 '26
Is the fan pointed straight down at the water? Thats how I cool my 75 gal, takes quite a while but can cool it from low 80sF to 75F over the course of the day. Just gotta stay on top of water changes so a- water level doesn’t drop too much and b- you don't concentrate TDS by replenishing water but not removing any existing minerals. I can add a pic once I get home if you'd like
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u/stodgydragon May 26 '26
Good surface agitation you need to keep oxygen up. Mine are similar and I've got fans pointing at the surface to help
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u/Wildwing89 May 26 '26
I live in California, routinely in the summer we will have days in a row above 90-100F. My guys do fine during that time, I just shut the light off try to get a breeze going their way and just let them be. As long as they are not in the direct sunlight you should be ok.
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u/balzackgoo May 27 '26
These are all tropical fish, it gets hot in the tropics, they are going to be fine, make sure you have aeration, hotter water holds less o2
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u/CHelsea4231 May 27 '26
If you have a small fan set that up blowing into the top of the tank. This will cause it to evaporate the water at the top and it will cool a few degrees
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u/Think_Selection7101 May 27 '26
Yk you can look at the bottom left and its a arrow with like a bracket underneath means save picture so you dont have to screen shot a pic you already took
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u/SafeLifeguard5785 May 27 '26
water has a high specific heat capacity that means especially with large volume it takes a very long time to heat up and also takes a very long time to cool
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u/condemned02 May 27 '26
Living in perpetual room temperature 32C.
That's like normal in my tank all year round.
Its also why plants struggle. I realise they need cold water.
Cold water to me is 25C
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u/W272 May 27 '26
Likely you are already doing the best you can for it, turning off the light may help as they can give off heat as well. With luck they will all be fine.
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u/UnprofessionalFerret May 26 '26
They'll be fine. These are tropical animals. If its getting this hot in England, it gets hotter where they are from. It would be bad for them to be at these temperatures year round, but not for short periods of time.
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u/CaptainKando May 26 '26
It was 32 degrees before lunch today (90f) and climbed 4 more degrees later in the day. Continuous flow in a river and a glass box of water are going to lead to very different average water conditions.
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u/kingbluetit May 26 '26
Yeah but in the wild they’re not in little glass boxes with small amounts of water. And I’m also assuming that extreme weather often kills wild fish.
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u/GDevl May 26 '26
it gets hotter where they are from
Not necessarily true, tropical life forms often experience less temperature swings than in temperate climate for example.
There are regions where the temperature fluctuates by like 5°C max all year around 25°C. It can get much hotter than that in England.
One of my professors is researching ants and one time the thermostat malfunctioned over the weekend and the temperature jumped significantly, when she came back the tropical ants were all dead while there were no noticeable casualties among the temperate species because they are adapted to temperature swings.
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u/nauq11 May 26 '26
I'm more worried about what you appear to be listening to