Why Does Molly Fish Stay at The Bottom of The Tank?

Since Mollies require more oxygen, they should ideally swim in the middle or at the top of the aquarium. Therefore, the fact that a molly lies unmoving at the bottom of the tank raises concerns that something may not be right. And your suspicion could be correct!

A molly bottom of the tank

There are multiple possible reasons that a fish might be motionless at the bottom of the tank, some of these include swim bladder disease, Ammonia poisoning, pregnancy, fin rot, or Ich disease.

All of these points are explained in this article so keep reading to find out!

Reasons for Molly Laying Motionless at the Bottom

1. Ammonia Poisoning

Your ammonia might be laying motionless at the bottom of the fish tank because of ammonia poisoning.

Your mollies will try to get away from the discomfort caused by the high ammonia levels in your tank by running to the bottom. If there is a large concentration of nitrites and nitrates, the same thing will take place.

You should test your water for pollutants, preferably once a week. Your greatest choice in that regard is the test kit. You may also see symptoms in your fish’s behavior, although they appear once the condition is about to be too late.

Ammonia Poisoning

The ideal fish tank water has 0 PPM of ammonia and 0 PPM of nitrates and nitrites. You can purchase a water testing kit from your local pet store or online.

If the ammonia levels are high you should perform water changes. You have to change 50-60 percent of the water in the fish tank to bring the ammonia and nitrate levels to zero.

2. Swim Bladder Disease

Every fish has a swim bladder, which is an organ that keeps your fish afloat. However, for different reasons, it shifts, which causes mollies to lie immobile at the fish tank’s bottom.

Constipation or overeating are the primary causes of swim bladder disease. As a bloated stomach might result from eating too much, pushing the swim bladder to the side. Due to this, the molly will find it difficult to keep afloat and will eventually sink.

Swim Bladder Disease

If your fish Is suffering from swim bladder disease you can cure it by moving it to a different fish tank. For the first 48 hours, don’t feed the sick fish anything to give her time to process what is already in her digestive system. The fish will eventually get back to normal throughout this period.

If that doesn’t work, use a salt treatment, and put one tablespoon of aquarium salt for every five gallons of water in the molly’s recovery tank. Use aquarium salt made specifically for freshwater aquariums as bacteria that cause swim bladder disease are eliminated by the salt.

3. Pregnancy

Mollies are livebearers, meaning they deliver live infants. While it doesn’t always happen, pregnant molly fish have been observed to frequently visit the tank’s bottom. They may even spend several days there at a time.

Growing Belly

If your molly is a female, you should also keep an eye out for extra symptoms such as a bloated tummy. Mollies that are pregnant also move more slowly. They shun their tank mates and eat more. A dark triangular mark can be seen close to the anal vent if you look closely.

Pregnant mollies look for hiding spaces. So you should provide as many hiding places for your molly as you can, or move it to a nursery tank until your molly gives birth.

4. Fin rot or ich Disease

Because it causes white spots, Ich is a condition that is relatively simple to recognize. It is a painful condition. It is common to observe mollies that have contracted ich rubbing their bodies against rough surfaces. This is one factor that could account for your molly fish’s decision to stay at the bottom for so long.

Fin Rot

Your mollies may feel less uneasy and start rubbing up against items at the bottom, such as rocks and substrate as that might relieve the irritation. Ich is probably to blame if your molly fish continually rub up against the substrate near the bottom.

Curing fin rot is not that hard. We advise using erythromycin since it is a broad-spectrum antibiotic and efficient against fin rot. Methylene blue is a potent antifungal remedy for fish with a secondary fungal infection.

5. Uneven Temperature

Temperatures above the recommended range will cause pain in your fish. Warm water has less oxygen than cold water. A temperature increase could cause an oxygen deficit.

Uneven fish Temperature

This will force some fish to seek refuge at the tank’s apex. It is also worth mentioning that a temperature increase might cause warm water to rise. This results in the formation of a layer of cold, oxygenated water at the bottom. Molly fish will go to this area of the tank to relieve their distress.

Verify your tank’s temperature. Turn the water temperature up to at least 80 degrees if you have a tendency to keep it on the colder side of the suggested range of 70 to 85 degrees Fahrenheit for mollies. Your entire molly community will likely benefit from increased warmth because low temperatures can create gastric problems in fish.

6. Mollies feel tired due to Aquarium lighting

The purpose of aquarium lights is to create a night/day cycle in your tank. After a while, you’ll notice that your fish sleep exclusively when the lights are turned off. However, leaving the lights on may hinder your mollies from falling asleep.

They will eventually display signs of weariness during the day. This includes occasionally sinking to the bottom. This is more likely if the aquarium is exposed to lights in the late evening.

7. Stress

A lot of things might create stress in molly fish. Poor water quality, aggressive tank mates, and new habitats are all examples of this. When you first introduce a new aquarium to a fish, it may become disoriented.

molly stress

Others will be irritated by new lighting, unexpected motions, or changes in decor. These responses will drive them to seek refuge at the tank’s bottom. You should be wary if you’ve recently made alterations to your aquarium.

How to Prevent Mollies from Lying on the Bottom?

Do not jump to conclusions quickly as your fish could be sleeping or napping. If you look closely enough, you will notice that a fish, when sleeping, moves its fins to stay afloat and upright, so make sure you inspect the condition of your fish thoroughly before trying any treatments!

1. Ensure Proper Water Conditions

Maintain ideal conditions in your molly tank. To minimize congestion, get an aquarium of at least 10 gallons. Keep the temperature between 72 and 78 degrees Fahrenheit, and the pH between 6.7 and 8.5.

Keep a testing kit on hand at all times. In general, you should monitor the tank’s temperature, pH, ammonia, nitrate, and nitrite concentrations.

Set the fish Water Parameters Correctly

If contaminants are the source of the problem, replace one-third of the tank’s water every week. Identify and remove components that increase the concentration of toxins, such as dead plants and decomposing leftovers.

2. Filtration

I strongly urge you to invest in a filter if you don’t have one. it will keep the water clean and you will not have to worry about changing the water yourself.

This is not to say that you won’t be changing the water at all. You have to clean your tank every 2 weeks to avoid causing ammonia poisoning. You should also clean the walls of the fish tank while you are at it this will avoid algae build-up in your fish tank.


3. Remove Tank Mates that Harass your Molly

Aggressive tank mates are a common source of stress in fish. Remove any other fish in the tank that are disturbing your mollies if you don’t want them to hide at the bottom. If it isn’t possible, relocate your molly fish to a separate tank.

If that isn’t an option, add some plants and decorations for your mollies to hide from their hostile tank mates. Make every effort to maintain a tranquil environment in the tank.

4. Proper Lighting

Create and maintain a consistent day/night cycle for your molly fish. You should get an automatic light. You won’t risk depleting your mollies by leaving their lights on at night. Automatic lights will turn on at night and off in the morning whether you are present or not.

The Bottom Line

Molly fish laying motionless on the bottom of the tank is almost always a result of some issue, although there are a few exceptions (like pregnancy). you should keep an eye on your molly fish’s health and look out for diseases if you notice it laying on the floor.

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