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The Daily Insight

Do mollies live in schools?

Author

Sophia Hammond

Updated on February 15, 2026

Do mollies live in schools?

Mollies are active and social so they enjoy schooling together. A shoal should be predominantly female since males are known to harass and stress females.

Can Mollies school with other fish?

Mollies are friendly, peaceful fish that generally get along with their tank mates well. These fish are social and like to be kept in schools. They will grow depressed and isolated if kept alone and should have at least a few other mollies in the same tank. They do best when kept in the company of other live bearers.

How long should you isolate an aggressive fish?

Keep the fish isolated for at least a week or two, the longer he is separated the better. This will give everyone else the chance to rearrange the hierarchy, become more dominant, settle into the tank, and gain confidence.

Are molly fish fin nippers?

Yes, mollies are fin nippers. Despite being peaceful and friendly, mollies are notorious for being fin nippers. Male mollies especially love nipping the fins of other males to establish their dominance and defend their territory. Mollie fish also tend to nip at other fish with large, flowing fins.

How do I stop my molly fish from fighting?

One of the easiest ways to stop males fighting is to get the male-to-female molly ratio correct. Ideally, you want one male molly for every 3 or 4 female mollies. If you just have a group of four fish and only one is male, there will be little to no fighting.

How big do sailfin mollies get?

Sailfin mollies are small fish. At one year of age, males typically range in size from 0.5 to 3 in (13 to 76 mm) SL, while mature females are likely to be 0.5 to 2.5 in (13 to 64 mm) inch SL. The size of adult males is directly correlated with population density.

Are mollies fin nippers?

Yes, mollies are fin nippers. Despite being peaceful and friendly, mollies are notorious for being fin nippers. Male mollies especially love nipping the fins of other males to establish their dominance and defend their territory.

Will mollies school with guppies?

Yes, guppies and mollies can live together, and they actually work well together. However, if the right requirements aren’t met, then some aggression may occur (from the mollies.) And there is always a slight risk that mollies will nip fish that have long fins such as guppies.

How many mollies Can I put in a 20 gallon tank?

The average molly fish will grow to a size of 3 inches. Keeping three female mollies and one male molly fish together is the best option in a 20-gallon tank. They are livebearers, so keep an eye out for babies on a regular basis.

How do you calm down an aggressive fish?

Here are some tips to help you deal with the aggressive fish in your aquarium.

  1. Use a Net to Separate the Fish.
  2. Rearrange Your Aquarium Decoration.
  3. Add New Hiding Spots in your Aquarium.
  4. Separate Your Passive Fish.
  5. Isolate the Bully.
  6. Get a Bigger Aquarium.
  7. Move the Aggressive Fish into a Different Aquarium.

How do I stop my fish from biting my fins?

Treat injured fish with a fin rot solution to heal nipped fins and prevent infection. Open wounds attract bacteria and can quickly turn into a case of fin rot when fish are stressed. If an aggressive fish is chasing a passive fish and nipping at its tail constantly, it will become stressed.