# Water temperature - huge effect on balance in 24 hours



## Franks (19 Mar 2021)

During my re-scape setup, I reused my extremely mature canister filter and media and added a new clay-based substrate. Dialing in the Co2 and balancing liquid ferts, while tuning the lighting and all was looking good within a few days i.e. plants showing new growth and generally pearling - I had no heater at the time and the water temperature was ~20degC ambient.

I then added a heater set to 22degC but it seems that this would increase the water temperature to anything between 23-25degC - not very accurate I know and probably because it's a cheap 200w heater in a 155L tank. The next day, I had an attack of brown algae/diatoms, certain plants started melting (especially the AR) and within a few more days, the brown algae went crazy and all healthy plants stopped pearling! I'm still addressing and slowly winning the brown algae fight with bi-daily 50% water changes and leaning out the dosing regime until the plants really take hold and recover. I noticed that when I was changing the water, the temp would drop drastically back to around 17-18degC, and then the next day it was back to 23-24degC due to the heater. Noticing this swing in temperature, I turned off the heater and carried on with my bi-daily 50% water changes, and now with a much more stable lower temperature, all the plants are getting new growth, pearling and the brown algae is receding even further - this is within 24 hours! The ambient temperature of the tank is much more stable and seemingly a better-balanced environment at 20degC. 

I'm now a little worried about my livestock, 4 Otto's, 2 Angels and 12 Black Neons. They are feeding great, still really colourful and seemingly unbothered by the 20degC water temperature, yet all the advice online is for the water to be between 22-26degC. Should I be worried - or is this one of those "it's always been recommended so must be true" folklores? There are a number of recent statements from professional aquascapers stating they don't use a heater at all and often keep their scapes with tropical fish at the low end of the temperature spectrum, some also mentioning 20degC temps being perfectly fine, this also goes hand-in-hand with Tom Barr also reporting that the difference in gaseous retention in the water column is huge over the 10degC data-points we tend to keep our tanks at. I also once kept an aquascape at 28degC with blue neon tetra and German blue rams and was constantly in battle with BBA, green spot, string algae, and then finally Cyanobacteria which caused me to tear down the tank. GreenAqua recently laughed at someone trying to keep a scape at a temp upwards of 26degC because they feel you must be fighting a losing battle from the start. 

Any thoughts? I'm inclined to give it a week to see what changes unfold.


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## Zeus. (19 Mar 2021)

Try and keep mine at 22 degree max, does creep over that in summer, when doing WC in summer I dont even mix with hot water accepting the water as it comes from the tap which can be at 15 degrees. If the water flows though my shower mixer tap with the hot feed turned off I use it


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## Nick potts (19 Mar 2021)

I keep all my tanks (except 1) at room temp, which for me is stable at 21c.

There are certain fish I would not keep but I have ottos, ember tetras, a few cory species all doing fine, always eating and fat and healthy. I couldn't say if long term these temps would be detrimental though.


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## Franks (19 Mar 2021)

That's great to know - thanks for the input chaps. I'll monitor the changes feeling a little more reassured. To be fair, this is in a cooler room of the house and during Spring/Summer months, it'll get much warmer so I'd expect the water temp to naturally rise to 22-23degC.


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## Sammy Islam (19 Mar 2021)

Franks said:


> That's great to know - thanks for the input chaps. I'll monitor the changes feeling a little more reassured. To be fair, this is in a cooler room of the house and during Spring/Summer months, it'll get much warmer so I'd expect the water temp to naturally rise to 22-23degC.


In a proper heatwave your tank will probably reach 28°C+


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## John q (19 Mar 2021)

Not so sure you'll have long term success with the angels at that temp tbh. I guess time will tell.
I would imagine the professional aquascapers that keep really low temperature tanks often only introduce the likes of Angelfish and rams on a short term basis.


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## MichaelJ (19 Mar 2021)

Hi @Franks 

20C (68F) for angles and black neon tetras that is definitely the lower end (if not outside) of their preferential temperature range  - even if not totally comfortable they will probably survive though, but I would bump the temp to 22C (72-73 F) and still get most of the benefits with respect to algae growth that are mentioned. I have angles and black neon as well (and a bunch of other tetras and rams) in two heavy planted tanks and I keep them at 26-27C (79-80F) and they all show great colors, fitness and behavior - of course. numerous other factors play into that, as for algae growth, besides water temperature.  I do have algae growth (hair algae) on some sword leaves and Hygro’s that are close to the surface and probably gets a bit too much light - I usually just trim those to make room for new growth.

Cheers,
Michael


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## Karmicnull (19 Mar 2021)

just to add to the confirmation that lower temperatures are often ok, take a look at <this article> from seriously fish


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## MichaelJ (20 Mar 2021)

Karmicnull said:


> just to add to the confirmation that lower temperatures are often ok, take a look at <this article> from seriously fish



Interesting article that makes a lot of sense. I think it's safe to say that it depends on the livestock.

FWIW here is a paper out of National Institute of Amazonian Research et. al. which at least suggest some upper and lower bounds for Cardinal Tetras (specific to shipping in the trade) which set the lower bound at around 20C (where morality rate starts to go up significantly):  Tolerance to temperature, pH, ammonia and nitrite in cardinal tetra, Paracheirodon axelrodi, an amazonian ornamental fish

Cheers,
Michael


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