Are temperatures above 85°F safe for breeding guppies?

[Abby W]

My female guppies are very pregnant, and I had a coworker tell me today that I should hike the temperature up so it's near or above 90°F because they like to give birth in warmer water. I currently have them in a planted 10 gallon at 82°F. I thought that 82 was high, and I've even shut off the tank's heater since the weather has been so hot and the tank has stayed consistently at 82. Are temps above 85°F safe for them, and would it be beneficial to turn the heater back on?

Edited August 31, 2022 by Abby W
Added image.

[Scapexghost]

I wouldn't change the water params in any way while fish are pregnant. A big change can lead to a failed pregnancy. If the fish is comfortable getting pregnant at these temps she'll be comfortable giving birth at these temps. Guppies give birth year round so i wiuldnt think temp plays any role. In general i would avoid keeping guppies above 86°.

[SimmonsSnailsNScales]

I agree with @Scapexghost. Whatever temp you feel comfortable with you should be able to leave it alone. With most fish I have found consistency is key.

[Cinnebuns]

Your co worker was wrong. Yes higher temps speeds everything up in fish, including shortening their lives, but you need to change as little as possible when a guppy is about to give birth AND this is too high for a guppy to be comfortable. I'm glad you didn't go to 90!

I do agree with @Scapexghostand @SimmonsSnailsNScales tho that lowering it now is not a good idea. They are vulnerable right now and need consistency and predictability. Guppies are an amazing ability to control their pregnancies. Even without getting into the AMAZINGNESS of cryptic female choice (is serious the weirdest and coolest!) they have unique control over when they give birth. They can hold their fry in if they do not feel safe which in extreme cases can lead to death. They are also able to abort their fry. These are scenarios you are looking to avoid by reducing their stress as much as possible. 

I can go more into depth if you want but I don't wanna assume you don't already know it as much as I already have lol. Lmk if you would like some tips for reducing stress of a female in labor and I can get you some!  

[Jenja]

Beautiful fish! Glad you didn't raise the temperature, it would have been detrimental to your plants as well as your fish (I've never even seen 90 advised for fighting ich...I'd probably be asking how old is your co-worker's oldest fish, bet it is well below anticipated lifespans if they give advice like that).

[lefty o]

ideal for guppies is 72-76 do not crank the heat up, your co-worker is nutz! they will survive fine in the low 80's, just keep them oxygenated (air stone, moving water on the surface etc).