6 Possible Reasons Why Your Molly Fish Is Shaking, And How To Fix It

Fish are very unpredictable because they could exhibit some funny behaviors you haven’t seen before all of a sudden. All fish has their elements of surprise, which could get you puzzled. In this article, we will discuss the issue of Molly fish shaking. Molly fish are active and colorful tropical freshwater fish, although they are hardy, sometimes they could be shaking or shimmying, as you may call it, and there are reasons for that, which we will discuss in this article and the possible solutions.

Why is my Molly fish shaking? A Molly fish could be shaking because the water temperature is not suitable for its body or it is Stressed.

Sometimes in fish keeping, problems might arise which could surprise you, especially when your fish starts exhibiting behaviors that you haven’t seen before such as this one.

Although the above reasons are just a few reasons why your Molly could be shaking its body or shimmying as you may call it.

You will agree with me that fish shaking its body is not okay or normal, but in some cases, it is normal, because some fish shake when they are about to mate, and they use it to attract the opposite sex, and some shake for simple reasons that means nothing.

But in the case of Molly fish, it means a lot, especially if it continues to shake without stopping for long, then I think you have something to worry about because it is not normal.

Why Is MY Molly Fish Shaking?

If you find out that your Molly is shimmying, then here are the possible causes.

1. Stress: Mollies are very active and lively fish, in fact, they act as agents of stress themselves because they could stress other animals and slow fish in their tanks.

Upon that, they despise getting stressed themselves, in fact, no fish like getting stressed, because, it could affect their overall health.

Many factors could stress them, some of them are poor water quality, small tank size, bullies or aggressive tank mates, poor male/female ratio, toxins in the water, temperature, etc.

All these could lead to stress, and stress could lead to them shimmying.

Stress could easily kill any aquatic animal, including fish, and it shouldn’t be taken for granted.

So, if your fish is shaking, then it may have been stressed by any of these factors above.

2. Wrong Temperature: Every animal has their specific ideal temperature, and Mollies are no exemption.

They are tropical fish, and also freshwater dwellers.

Being tropical fish means they could only dwell in a moderate type of water, that’s a type of water that is neither cold nor hot, but kind of warm or normal. ( moderate)

Their ideal water temperature is 72-78°F, although they could be alright in a 68-80°F, only if the temperature is steady, and not fluctuating, for instance, today it will be 68, tomorrow it will be 75°F and so on. Fish doesn’t like it.

This is one of the reasons why every fish needs a Heater, especially fish like the Molly fish, to keep the temperature moderate and steady too, for their health and benefits.

So, if your fish is shimmying, you might have to check the water temperature and maintain a moderate temperature if it is not okay.

3. Toxins in the water: Toxins or chemicals that usually form in the water as a result of dirtiness which is caused by poops, decayed matters, etc could be very harmful to your fish, and might cause this type of behavior in them.

Toxins or bad chemicals like ammonia, nitrites, nitrates, chlorine, etc are very harmful and could be fatal too.

Once they breed or form in a tank, they will become a major source of stress and frustrations to your fish and other aquatic animals too, and it could make them to be shaking.

So, you need to get yourself a water testing kit to be on the safe side.

4. Inappropriate Water Chemistry: This is one of the factors that could cause your Molly fish to start behaving in such a manner.

This happens when they find themselves in a tank with the wrong water pH and wrong water parameters too.

The ideal water parameters for mollies are-

6.7–8.5 pH

Water hardness:

15–30 dkH

So, when they happen to find themselves in a type of water that doesn’t have the right pH and hardiness, as described above, they may get stressed and might even die.

The wrong pH could burn the skin of a Molly fish, so, wrong water parameters could be the reason your Molly is shimmying.

5. Uncycled tank and Small tank size could be another great reason why such a thing might be happening to your Molly fish.

A single Molly fish requires up to a 15-gallon tank that is well cycled.

When the tank is small and uncycled, it will only do these things to the fish, it will breed aggression and stress, and some other things.

We all know that stress is one of the main factors that could make your fish to start shaking, so tank size and tank cycling could cause stress, which could in return lead to your fish shaking.

6. Diseases: Some Bacterial and parasites could infect fish and cause them to be behaving in such a manner.

Many diseases could affect Mollies, despite being hardy fish, and get them down, which as a result could lead to them shimmying.

People used to blame shimmying on what they call livebearer disease and other diseases too.

Now you know the 6 possible reasons why your Molly may be shaking, now let’s look at the possible solutions.

How Do You Fix Molly Shimmy?

To successfully fix your Molly fish from this, first, you have to find out the main reason why it is twitching, and then fix it accordingly.

1. If your Molly fish is twitching or shaking as a result of Temperature, what you will do is, get a heater and keep the water at a moderate temperature that fits the fish.

Once this is done, the fish will once again become normal.

2. If this is happening as a reality of stress, then relocate every aggressive tank mate in the tank and check for any toxins or chemicals in the water and once you detect any, do a change of water, at least 20-50% every day, depending on the level of the toxins until they are neutral.

Make sure your tank is very sizeable and could contain the number of Mollies you can keep, as a Molly fish will need up to a 15-gallon tank.

Also make sure your tank is planted, because live plants could neutralize some of the harmful toxins.

3. If this is a result of diseases and sickness, then your best shot is to get a veterinarian doctor involved, as we don’t advocate for self-medication here.

4. Always keep your tank clean and also make sure you buy a filter for your tank, to help reduce the number of poops and other dirt in the tank.

5. Adjust to their ideal water parameters, and also make sure your new aquarium is fully cycled before getting any live animal in it.

6. Change the water at least once every week and clean the tank, but, don’t forget to rinse the tank very well, as some detergents could be harmful to fish too.

Again avoid spraying perfume and insecticides, etc near your fish tank, as they could be very harmful to their health.


Now you know why your Molly fish may be twitching, shaking, or shimmying, as you may call it, and the possible tips to stop or control this, so good luck.