Betta Imbellis Overview and Care Guide

Betta imbellis is part of the Betta splendens complex. It is native to Southeast Asia and prefers the sluggish, shaded waters of ponds, swamps, streams, and rice paddies with muddy and leaf-debris bottoms. 

Its name ‘imbellis’ is derived from Latin, meaning peaceful. This Betta is also called the Penang or the Crescent Betta. 

Betta imbellis is gaining in popularity due to its more docile nature. 

If you’re interested in Betta imbellis, read on for some information, fun facts, and pro tips about keeping this fish happy and healthy with our overview and care guide. 

betta imbellis


Appearance of the Betta Imbellis

When someone mentions a Betta fish, we may conjure up images of long, flowing fins and brightly-colored hues. However, the Betta imbellis is different.

First off, you will notice this type of Betta fish does not have those classic long fins. In fact, imbellis is also known as the “crescent” Betta because its tail fin is (you guessed it) crescent-shaped. The other fins are also short and rounded. 

The scales and fins of imbellis are typically metallic with shades of green, and blue with deep red on their tail fin.

Full-grown males will reach maturity at about one year old and will be between 2 and 2.5 inches long. Females reach maturity between 6 and 7 months old and generally have shorter fins and are more brownish (this provides them better camouflage in their natural habitat).

Betta Imbellis Tank Requirements & Setup

Like all Betta fish, we recommend at least a 5-gallon tank; however, 10-gallon is a better choice for the Betta Imbellis species as it is an active fish that likes to spend most of its time in the middle to top areas of the habitat. 

Betta Imbellis needs a well-planted tank (live plants) to provide plenty of shade for hiding and resting amongst. Tall, leafy plants such as the Amazon Sword, Anubias, and Ludwigia make excellent coverage for the Betta tank

Since this species does enjoy a dimmer atmosphere, you may also want to choose the addition of Indian Almond leaf which will add beneficial tannins to the environment and will naturally darken the water.

Even though Imbellis does prefer slow-moving waters, you will still need to add a filtration system to the tank. However, be sure to choose one with a sponge intake and an adjustable (or slow) flow-rate

The Betta Imbellis is a good jumper, so be sure to have a hood or lid on your aquarium to keep him safe and sound. Placing a top on your aquarium will also help keep the heat inside. This will also be accomplished by using a submersible heater preset to between 70 and 82 degrees Fahrenheit. 

For maintenance of the Imbellis habitat, remove 25% of the water every two weeks. Use an aquarium vacuum and gently go over the substrate (if using gravel or sand) to remove debris and fish waste. Replace with treated water at the proper temperature to avoid shocking your fish.

Pro Tip: Use an aquarium thermometer to get the temperature of your tank and replacement water just right. 

Feeding the Imbellis Betta

Betta fish are carnivores and dine on a variety of insects, larvae, and other invertebrates, as well as fallen leaf litter in their natural habitat. 

For us to duplicate this as best we can, feed your Betta Imbellis a varied diet consisting mostly of high-quality flake and pellet foods. Once-a-week supplement your fish’s diet with frozen or live foods such as bloodworm, daphnia, and brine shrimp. 

Pro Tip: Do not overfeed your Betta. This can lead to constipation, bloat, and even death. To avoid this, feed small amounts (two pellets) twice daily or as much as can be consumed in a minute.

Compatible Tank Mates for Betta Imbellius

Even though the Imbellius is a peaceful species of Betta fish, it can still show aggression. This is especially true if the tank is too small and overcrowded. 

Follow the rule of aquarists of 1-inch of fish per gallon of water so you can avoid overstocking your tank. 

Compatible tank mates for the Imbellius include:

  • Neon Tetras
  • Ember Tetras
  • Ghost Shrimp
  • Guppies
  • Kuhli Loaches
  • Female Imbellis Bettas (10-gallon minimum)

Breeding the Betta Imbellis

As with all Betta fish, the male Imbellis is a bubble nest maker. He will blow small bubbles at the top of the aquarium (sometimes by taller plants as an anchor) when he is ready to spawn. Once the nest is finished the pair will lock themselves in an embrace and the female will release her eggs. The male will fertilize them then begin to relocate the fragile eggs to the bubble nest. 

You can remove the female to her own tank, then watch as the male continues to care for the eggs. If one falls from the nest, he will quickly scoop it up and secure it back into the bubble nest.

About 48 hours later, the fry will begin to hatch. It’s at this point that you will want to remove the male (so he isn’t tempted to eat them) and allow the baby Betta to develop. 

Feed the fry a liquid diet (made specifically for Betta fry) for a couple of days, then switch over to baby brine shrimp and microworms.

How to Choose a Healthy Betta Imbellis

Like any fish, you will want to observe the Imbellis at the breeders or pet retailer. Look for healthy fins and scales (no rips, tears, or discoloration) and watch the fish for its activity level. Is it swimming and exploring its environment? 

Avoid purchasing a fish from a tank where dead fish are present or ones where the fish are inactive and sickly, there are white spots on the body and face or rapidly moving gills. 

If your Imbellis is living in a cup it will be more difficult to get a gauge on its overall health, but still, be sure to look at its body and fins for any signs of illness. You may also gently tap the cup to ensure it will respond. Fish lying on their sides or gasping at the surface are in distress and need immediate attention. 

Before you purchase your Betta Imbellis, ask the breeder or retailer if there is a guarantee of the health of the fish. You may be asked what conditions the fish is entering into (to help ensure the success of the rehoming). Some breeders and retailers will give you your money back within 24 or 48 hours of purchase should your fish “not make it.”

Common Betta Imbellis Diseases 

Even though the Betta Imbellis are quite hardy, they can still get ill. Fortunately, most diseases of this species are due to poor water conditions. Be sure to perform regular maintenance on your aquarium to help prevent the following diseases and keep the pH levels and temperature consistent. 

Pro Tip: Always quarantine new tankmates for at least 14 days before adding them to your Betta tank. This helps ensure they are healthy and will not spread a disease to your Crescent Betta.


Constipation is a common ailment in the Betta species. This can be caused by overfeeding or by feeding the wrong type of food. 

The Betta tend to be gluttonous fish and will continue to eat as long as the food is available. For this reason, only feed your Imbellis a couple of pellets twice a day, or what it can consume in one minute (for other types of foods). 

You will also want to add live foods to your Betta’s diet. These foods naturally contain fibre which will help keep your fish “regular.” Daphnia and larvae are good sources of live food for the Imbellis.

Another source of constipation is the lack of exercise. Like all animals, your Betta needs exercise. However, this will be difficult to accomplish in a tiny container. That is why we recommend a minimum of 10 gallons for a Betta Imbellis.

Other ways to help prevent constipation in the Imbellis are to be sure to perform regular tank maintenance by scooping up all that uneaten food, keeping the temperature warm to encourage good digestion and exercise, and feeding your Betta a cooked, deskinned pea every couple of weeks for some added fibre. 

Symptoms of Constipation

  • Stringy feces
  • Legarthy
  • Not swimming
  • Spitting food out/not eating
  • Bloated stomach

Fin & Tail Rot

Fin and tail rot in Betta fish is a common, albeit, preventable disease. These bacteria naturally exist in your aquarium and can become an issue when the temperature is too cold (well below 78 degrees Fahrenheit), and the water is allowed to become polluted with high levels of ammonia, nitrate, and nitrites caused by uneaten food and fish waste. All these factors combine to increase your Betta’s stress level, leading to weakened immunity. Overcrowding your Betta habitat can also lead to poor water conditions.

To prevent fin and tail rot perform regular tank maintenance and be sure not to overfeed your fish. Keep stress to a minimum by not overcrowding your tank and maintaining a good temperature of between 75 and 80 degrees Fahrenheit. 

Symptoms of Fin & Tail Rot

Check your Betta for signs of this illness by examining the top (dorsal) fin, tail (caudal) fin, and the bottom (anal) fin for the following symptoms. 

  • Mild Fin Rot – jagged fins with brownish edges and whitish tips or spots.
  • Moderate Fin Rot – large, receding deterioration of the fins, black or bloody edges of the fins or the fins may develop fuzzy growths.
  • Severe Fin Rot – bloody fins with more deterioration or the loss of the fin entirely. Cottony growths on the body, body rot, lethargy, difficulty swimming. Death may be inevitable at  this stage. 

It is always best to treat fin and tail rot ASAP to avoid its advancement on your Betta. Left untreated, your Betta will die from this illness. 


This disease is caused by a single-cell organism that penetrates through the Imbellis slime coating where it will begin to eat the fish’s cells. It is also known as Gold Dust Disease, Rust, Oodinium, and Coral Disease. These names have sprung up from one of the main symptoms of the illness – the fish is covered by gold or rust-colored film over the entire body of the fish.

Other early symptoms of Velvet are;

  • Rubbing or scratching themselves against objects and the substrate (a sign of irritation and an attempt to dislodge the parasites)
  • The appearance of the gold discoloration
  • Lethargy
  • Loss of appetite

If caught in the early stages, Velvet is usually curable. However, once the illness advances, your fish’s chances go down for recovery.

Symptoms of advanced Velvet;

  • Cloudy eyes (looks like a film over the eyeballs)
  • Clamped fins (held close to the body)
  • Ulcers appear on the skin
  • Skin falls off
  • Bulging eyes

Always treat this disease ASAP to give your Imbellis the best chance of recovery and survival.

Betta Imbellis Overview and Care Guide Conclusion

If you love the Betta species and want a more peaceful specimen, then the Imbellis may be the one for you. This lovely Betta has beautiful iridescent scales and smaller rounded fins. It does need a larger tank (at least 10-gallons) but can be housed with other female Imbellis or suitable, compatible tank mates.

Like all Betta fish, we recommend providing the Crescent species with plenty of live plants and perhaps, even, an Indian Almond leaf for those beneficial tannins. Of course, he will also need a filter, heater, light, and regular tank maintenance to keep him healthy.

Unfortunately, you will also have to keep an eye open for some common diseases like fin and tail rot, velvet, and bloat caused by constipation. These diseases are both preventable and treatable, so be sure to practice good tank maintenance and do not overfeed your fish.

The Imbellis is an enjoyable pet, so we encourage you to bring one into your home aquarium.