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How Deep Should The Water Be For Betta Fry?

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As betta fry first grow in a bubble nest before becoming free swimmers, many aquarists wonder how deep their water should be. I personally asked this myself a few years ago, and I was pretty surprised by the answer.

Ideally, the water depth of betta fry should range from 8 to 12 inches. As a rule of thumb, it is better to have a broad and shallow tank than a narrow and tall one. That is primarily because betta fry swim horizontally, and shallow tanks will feature more room for swimming.

As we move forward, I will explain why getting a wide and shallow tank for your betta fry is better. Then, I will mention what tank I eventually picked, which was a huge success.

A male betta fish, taking care of the bubble nest he has carefully built.

Still curious? Feel free to check my complete guide on betta fish fry, where I discussed how to care for betta fry, what they eat, their growth stages, what equipment to use, and much more.

How Deep Should The Water Be For Betta Fry?

You can find breeding tanks in various sizes. The exact dimensions will depend mainly on the number of gallons you want. 

But the average retailer may not necessarily mention the depth. Instead, once you specify the size, they may ask you to decide whether you want a narrow or wide aquarium.

Narrow aquariums are also deep, but again, the exact depth will depend on the gallons. On the other hand, long or wide tanks are shallow. 

It makes more sense to invest in shallow tanks because they have a lot in common with the conditions betta fish encounter in the wild. They typically inhabit shallow water.[1]

You will find them in streams and ponds. They also prioritize horizontal movement (left and right) instead of up and down.

It is also worth noting that bettas have labyrinth organs that allow them to extract oxygen from the air. Therefore, if the water doesn’t have enough oxygen, they can always run to the surface.

But what does that mean for betta fry? They are smaller and more vulnerable than their adult counterparts. However, you are still better off keeping them in shallow tanks. They are less likely to thrive in deep aquariums. 

Take the following into account before you make your selection:

1. The View Aspect

The view plays a more significant role than some beginners realize. People keep bettas because of their long flowing fins and beautiful colors. And if you want the best view, tall, deep tanks are a great option.

Show tanks are tall and narrow. You find them in places that use aquariums as a decorative tool because they have large windows. Any passerby can observe the activities of the fish with relative ease.

However, you wouldn’t populate a show tank with betta fry. After all, it can take a baby betta up to nine weeks to develop its colors.[2]

Additionally, breeding tanks are not show tanks, as people use them to house breeding pairs. They will also hold the betta offspring once they hatch. 

You don’t need a large viewing window to raise betta fry. In that regard, a tall tank with a significant depth wouldn’t serve any purpose.

2. The Amount Of Dissolved Oxygen

Oxygen is probably the most crucial consideration in this discussion. Oxygen enters the aquarium through the surface. Devices such as filters can agitate the water to increase the oxygen exchange.

You can also maximize the oxygen exchange with a larger surface area.[3] This is where shallow tanks shine. 

Tall tanks are narrow. Their surface area is smaller, which is problematic because they are deep. You are more likely to record oxygen deficiencies at the bottom because of the restricted oxygen exchange. 

You cannot expect the betta fry to swim to the top whenever they need to breathe. The distance may exhaust them, especially if you have a large tank with a significant height. The fry will start to die gradually.

A shallow tank allows older betta offspring to survive at the top using their labyrinth organs, especially in warmer seasons where the high temperatures have lowered the oxygen concentration in the tank.

But keep in mind that the labyrinth organ is fully developed only after 3 to 6 weeks. Until then, you should do everything you can to enrich the water with oxygen. I discussed this more thoroughly here.

For more information on this topic, check out this article where I discussed the different growth stages of betta fry.

2-day-old betta fish fry, still hanging vertically.

3. Betta Fry Need To Move Freely

Many aquarists discourage the use of deep, narrow tanks because they limit the available swimming space. Bettas swim horizontally, not vertically. A shallow tank gives them more freedom because it’s wider.[4]

Narrow tanks will restrict their movements significantly. You could also crowd the tank by adding plants and decorations. 

Betta fish require plants and decorations to thrive. But their presence may do more harm than good if you have a narrow tank with limited space. The depth doesn’t serve any purpose. 

That being said, this is not a challenge at the start because the betta fry are so small. They can make do with the limited horizontal space in a deep tank for the first few weeks.

But they will eventually grow, and once their size exceeds the dimensions of the tall tank, you must move them to a broader tank. 

Admittedly, there are plenty of tall tanks whose width can accommodate growing betta fry. But they are pretty large, and larger tanks are not only heavier and more expensive, but they occupy a lot of space. 

If that wasn’t problematic enough, enormous aquariums could kill baby bettas because the creatures have to cross massive distances to reach the food.

The exhaustion will overwhelm them. You are better off sticking with a shallow and wide tank for the babies. 

4. Deeper Tanks Are Harder To Maintain

Have you considered the maintenance challenges a deep tank will introduce? Think about it. Betta fry eat a lot of food, and you have to vacuum the substrate to prevent the leftovers from rotting and poisoning the water.

What happens if the tank is so deep that you can’t reach the bottom with your arm? A shallow tank simplifies access.[5] Even if the aquarium is sitting on a table, you can reach every section of the fry’s aquatic environment.

You can overcome the limitations of a deep tank, especially if you hire experts to maintain it. But if you expect to clean the breeding tank yourself, a shallow, vast aquarium is the best option.

5. Shallow Tanks Can Hold More Plants

A shallow tank allows you to introduce more hiding spots in the form of plants and decorations. This is particularly important for betta fry in community tanks.

The hiding spots will keep them safe. You have less room for plants and decorations in a deep tank because they are incredibly narrow.

A male betta fish, looking after the fry that have just hatched.

6. Shallow Tanks Get More Light

You cannot trust deep tanks to expose the betta fry to ample lighting, especially during the first few days after hatching. 

An adult betta can just swim to the top section when the need arises, but a newly hatched fry may not have that kind of strength.

You can adjust artificial lighting to accommodate the tank’s needs, but that is not an option for tanks that rely on natural light. A shallow aquarium offers superior light penetration, not just for the fish but the plants as well.

Don’t forget: plants only produce oxygen when they have light. In the absence of light, the plants will absorb oxygen and release carbon dioxide.

What Tank Should I Choose For My Betta Fry?

The tank you choose mainly depends on the number of fry you have. As I previously discussed, betta fish can produce up to 500 fry, and when taken care of properly, about 90 percent will survive.

But in most cases, you’ll have a batch of up to 100 fry. These are the tank sizes I recommend depending on the number of fry:

  • Up to 100 fry – 10-gallon tanks.
  • 100 fry and more – 20-gallon tanks.

As for a 10-gallon tank, I personally went with the Aqueon Standard Glass Rectangle Aquarium (link to Amazon). It is pretty basic and quite affordable. 

It’s about 12 inches in height and 20 inches in length, which is pretty decent for betta fry. Of course, you’ll need to add a filter and a heater at the very least.

If your batch contains more than 100 fry, I suggest going with the Tetra Aquatic Turtle Deluxe Kit (link to Amazon). It was generally built with turtles in mind, but your betta fry will love this.

  • Here is an excellent Youtube video demonstrating how to transfer betta fish fry into a larger, brand new fish tank:

If you found this article helpful, these may also interest you:

Pro tip: If your betta fish breed frequently, you probably need to know a little about their eggs. You can find my complete guide on that topic here.


It is better to have a broad and shallow tank when it comes to betta fish in general and betta fry in particular. The water doesn’t have to be deep for the fry to thrive. Aim for 8 to 12 inches.

While tall tanks are more appealing in terms of viewability, they won’t benefit your fry. They will have less oxygen and won’t be able to swim freely.