How Long Can Molly Fish Live Without Food?

Say it’s your first time keeping molly fish and you’ve never been apart from them, but something comes up and in a few days you must go on a week-long trip.

Naturally, you’re worried about how your mollies are going to survive without food, especially if you don’t have anyone who you can ask to keep an eye on your mollies while you’re gone.

Or you have friends that could help, but they’re not the most reliable when it comes to undertaking responsibilities.


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So, you start wondering how long molly fish can survive without food. What happens if you don’t feed your mollies for a couple of days or a week?

Don’t worry, there are ways to prepare an aquarium and manage feeding even if you need to go away for a while. Plus, mollies can go without food for quite a while.

I will help you navigate these situations with the tips and tricks you can read about below.

How Long Can Molly Fish Go Without Food?

Adult molly fish can survive without food for up to 2 weeks. The same is not true for molly fry, which can only survive up to 3 days without food.

Still, you can’t just pack your bags and go, and hope for the best. There are things you must do beforehand to ensure that your mollies will be fine in your absence.

Let’s see how and what you should do.

How to Prepare your Aquarium Before a Trip?

Since you won’t be around to regularly check the aquarium, clean it and perform water changes, you’ll need to get a few things in order before you leave, namely:

  • Clean your filter;
  • Do a bigger water change;
  • Set the timer on your aquarium lights;
  • Clean the aquarium.

Let’s see how to perform each of these tasks:

1.  Clean the Filter

Notice that I wrote clean the filter and not replace the filter. This is important, because replacing the filter will disrupt the healthy bacterial colony in your aquarium, which will spell trouble for your mollies.

Therefore, a few days before you leave, do a regular filter maintenance. That is, rinse the filter in a bucket with aquarium water (never with tap water that has chlorine in it, which kills off beneficial bacteria!).

This if you have a sponge filter, if you have a canister or hang-on-back filter clean the mechanical filter and remove any built-up debris but avoid touching the biological filter to preserve the healthy colony of bacteria that has developed.

With regular filter maintenance, waste, debris and any built-up muck can be removed to prevent ammonia spikes in the aquarium.

2.  Perform a Bigger Water Change

If you do weekly water changes of 25-30%, the day before you live on your trip, do a 50-70% water change to remove as much waste and nitrates, and it will take longer for toxins to build up to dangerous levels.

Now, when doing a bigger water change, it’s advisable to add nitrifying bacteria to the aquarium to help keep the water chemistry stable while you’re away from your mollies.

3.  Set Lights on Timer

If you have live plants in your molly fish tank, you probably have a lighting system set up too. Ideally, you should have an aquarium light timer that you can set up.

What if you don’t have a timer and you can’t get one on a short notice? What you should do about the lights? Should you live them on? Should you switch them off?

I recommend switching off the lights rather than keeping them on 24/7, but your aquarium should not be in a dark room and it should get natural sunlight during the day.

4.  Clean Your Aquarium

It goes without saying that you shouldn’t leave without cleaning up the aquarium — remove decaying plants or leaves, dying or sick fish, and any uneaten food.

Ammonia spikes because of decaying matter and dead fish are common and you should do your best to prevent that while you’re not around.

Preparing your tank before you leave is one thing, but what should you do in terms of food for your molly fish? Should you invest in an automatic feeder, is it a good idea?

Should You Use an Automatic Feeder for Your Molly Fish Tank?

Automatic feeders do exactly that – dispense food for your molly fish automatically, so it’s not a problem if you’re not around to feed your molly fish yourself or there isn’t anyone who you can ask to feed them for you.

While they’re an excellent device for these situations, I won’t go so far as to recommend them for your adult molly fish.

Problem is that since you’re not around to perform water changes and do tank maintenance, molly fish that eat normally, will also produce waste that goes uncleaned.

For molly fry, however, things are a bit different.

How Long Can Molly Fry Go Without Food?

Since molly fry can’t survive longer than 3 days without food, an automatic feeder should be set up with powder food.

However, it’s important to strike a balance between feeding them just the right amount to keep them alive without polluting the water too much.

A small amount once daily will not do much harm to the water and keep them alive until you return home.

Your fry can survive longer even without food in a well-established aquarium that offers them soft algae and microfauna like seed shrimps and daphnia.

If your aquarium is fairly new, however, supplementing their diet with an auto-feeder is required.


As you can see, it’s not the end of the world if you have to leave your mollies for a few days without food. If tank conditions are good, mollies can live without food for up to 2 weeks.

If you have molly fry, set up a system to feed them once a day with a small amount that won’t lead to water fouling issues.

I hope you are now more at ease with leaving your mollies unsupervised for a few days, just remember to prepare the aquarium (perform a bigger water change and perform maintenance tasks) before you leave.

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