Topic: What water temperature do mollies need? Do I need a heater in my tank? I was wondering if I could get by without using a heater in my 20 gallon molly tank. I don’t want to buy a heater if I don’t have to. They are somewhat expensive. Need some help here. Thanks for your time.

*Awarded Answer
Posted by Chris W: These are some of my favorite fish to keep and I’m certain you will love them too. It’s important to properly research your fish before just going out and buying them. Good job doing the research part. You will be a great fishkeeper. Lets answer your question now.

Best Water Temperature for Molly Fish

Mollies are tropical fish and come from habitats that are very warm. Molly Fish need a water temperature between 77-82 degrees Fahrenheit. That means you do need a heater. When mollies don’t have adequate temperatures, they become very sick. The sickness usually starts with an ich sickness breakout throughout your entire aquarium. It’s very important to take proper measures to making sure your water temperature stays between that 78-81 degrees Fahrenheit.

Do Molly Fish Need a Heater?

Molly fish tanks do in fact need heaters. Your water needs to be between 78-80 degrees Fahrenheit. We recommend you buy a heater to the size of 5 watts per 1 gallon of water of your tank size. We also recommend buying the eheim brand heaters because they are one of the best of quality and use less power than other brands. They have a larger heating element and work extremely effective. Here is a link and photo:

 

 

@Reply: I’m so incredibly sad but one of our female Molly’s has swim bladder problem and is upside down struggling to move at all. HELP PLEASE! Water parameters are fine but I did realize for some reason water temp was only 74. I unplugged and plugged back in the heater and it kicked on now. I had to remove the sick molly as the others were picking in her. She is in bucket and I’m trying to keep water warm.

@Reply: So I am waiting for my heater to come in from Amazon but my tank has dropped down to 70. Is there anything I can do or are my fish going to be ok until friday. I live in az where I usually dont have to worry about things staying warm.

@Reply: Ok here I go again is my Dalmatian Molly pregnant she’s acting weird staying by the heater and she’s already a big fish and I can’t tell if she’s squaring off or not. Trying to make sure I don’t have more surprise babies like yesterday. Which they all three are doing good the ones I was able to find and have been moved into my nursery tank

@Reply: Thanks for the add! I have 4 mollies, 1 male(black) and 3 females. I think at least one of the girls, black and yellow, is pregnant. Not a good pic of her, cause she doesn’t like to stay still.
I’m a bit confused on what to expect for how long their pregnancy is because internet is telling me everything from 20 to 60 days 😕 and I want to be ready!
Also, I just set up a 5 gallon tank for the fry for when they are little. Cloudy water still, but it will be cycled before babies are added and has a filter and heater. Any other recommendations on it?

@Reply: Looks like a lot of you are having fry soon… So, I thought I’d provide a home. One of our ladies anal vent/gravid spot to help give you an idea of things to look out for when your girls are close. Its not always this obvious, so keep your fishes dignity in mind when you lift up her skirt next time..
Notice she is also near the heater, which is common for females to do as they get closer to dropping fry. Hiding more as well as more aggression are also signs she is close.

@Reply: This fish has not moved from this spot by the heater for a half day. Not his normal behavior. The water is plenty warm. I’m wondering if he looks sick. His bottom lip seems to sort of hang open more than I remember, but that might be just in my head. The top of his tail looks like it might have something on it. Any suggestions? Our tank is coming up on one month old. Two other fish in the tank (molly and platy).

@Reply: What are you ammonia, nitrite and nitrate levels? Sounds like they might be high and he is stressed. If you cant test I would do a water change to help lower the levels to a more tollerable level

@Reply: Its nice to be able to do it at home so you dont have to go to the store each time. I test the most while cycling which is what your tank is doing now. Can you make it to the store to test today? Have you done a water change yet by sucking the debis from the rocks with a fish syphon?

@Reply: The syphon is hard at first but the more you do it it gets really easy. Just fill up the plastic wider end put the other end in the bucket on the floor. Let the water run threw the tube to the bucket for a second quickly submerge the plastic end and it should run…i had lots of trouble at first too lol. If its from petsmart and has a little flap so you can get it going by bobbing it up and down …thats what i had and I took that annoying peice out lol

Live Bearers question! I have 6 Molly fish and 4 very fat pregnant boxy looking females. So I put them in 4 floating breeder box, they get plant-based flake food in the morning and protein food in the evening.  Here’s the problem, it’s been 6 weeks in the boxes and no baby yet? Maybe they or uncomfortable or stressed and have a boarding or holding onto eggs. I don’t know😕

What are you planning to do with the fry? If you are just going to keep them. Release her in the community tank to have her babies naturally (hopefully you have a well planted tank with Java moss, water sprite, good coverage, etc… but if you don’t gets some acrylic yarn and make a safe haven for the fry) Are they balloon mollies?

not balloon mollies.  My big Community tank is new and planted but not growing in for good cover to hide in.

I have a 10 gallon fry grow out tank with lots of Java moss and guppy fry. I want to keep them all and have lots of full tanks.

the only thing I could advise is moving all of that Java moss temporarily to the planted tank. However, you might lose some babies doing this.  I’m interested how this will all pan out.

Honestly I would just release them. Even workout adequate plant coverage you’ll have more fish than you know what to do with very soon.

If you don’t have adequate plant cover for them yet, you can make artificial spawning mops.  Cory has a good video on it.

I have a male panda molly in my community tank who has always been a jerk. Because he was getting nippy with his tank-mates, I went out & got another 4 females thinking it would chill him out, but one by one he’s killed them. I just got back from 5 days out of town & came home to find he’d murdered the 3 remaining females & the other male is looking pretty beat up. He chases & nips at the non-molly fish, but so far he hasn’t killed any of them.  I don’t have this problem in my other tanks & I’m starting to wonder if I should maybe euthanize him because he’s turned into quite the serial killer! Does anyone have any advice?

I gave a molly fry away who killed off 6 of my brothers fish, ate 3 of his brothers and killed off a few fish 3 times his size I don’t believe in killing perfectly healthy fish, but when the fish turns out to be Hannibal Lecters best fish friend I have limits. Saving 1 fish to have 6 die is not good !

I was just thinking.., if the killer fish bred, would the offspring be hyper aggressive too ?? And the one I had wasn’t nippy, he was like a wild animal. Just killing everything in sight, then eating it.

I don’t know what the minimum size tank a single molly can go in, but maybe you should set him up like a betta, in a tank all his own. I believe they typically like a larger foot print, but maybe under the circumstances a 10g with a sponge filter, heater and a few plants.

I would not hesitate to introduce this fish to my special “big” fish tank which is currently stocked with one tiger Oscar, one Green Terror, and a juvenile Dovii X Red Tiger Motaguense hybrid.  This tank usually fixes them types of fish from hurting others.

I have a zebra danio that is the same way. Didn’t matter where I moved her to, she’d always terrorize the rest of the fish. I got shell dwellers a couple months ago and I decided to try her with them. Although they’re about half her size, they keep her in check with no problems. Now she can live out her days but she has a little army making sure she behaves. Maybe you could find someone who would take him in and put him in a tank like that.

PS – I had a whisker shrimp that did this to other shrimp, snails & fish. In da timeout tank he went! Wasn’t quite cycled fully, so unfortunately he didn’t live long. I was glad that I saved the lives of ‘the remaining ones’ and wasn’t too tearful about the ordeal.

I found him a new home! I popped into my LFS to replace my girls & was explaining the situation. They don’t do store credit or anything, but one of the employees said her mother’s tank is overstocked after a platy baby boom. I’m donating my serial killer to the cause! Lol