Is Raising Medaka Fish Difficult or Easy? What’s the Actual Difficulty Level?

This time, I’ll write about the topic of whether raising medaka fish is difficult.

Medaka are often described as easy to raise in care books, and they are raised in preschools and elementary schools, which is why they are considered beginner-friendly fish.

However, I believe many people might have found them surprisingly challenging to keep alive.

Based on my experience with raising various fish, I’ll explain the difficulty level of caring for medaka.

Raising Medaka is Easy!

Let me start by saying that raising medaka fish is relatively easy. Medaka are less prone to illness compared to other fish, and even if they fall ill, medicine can usually show immediate effects.

Goldfish, on the other hand, often succumb to mysterious diseases that aren’t even documented in books and don’t respond to medication. Also, unlike bettas, which tend to fight and can’t be housed together, medaka can live harmoniously in groups.

Since medaka have small bodies, water changes aren’t needed frequently, and they can be raised in small tanks. In a density of one fish per liter, they can live without aeration.

Therefore, medaka can be considered an easy fish to care for.

Susceptibility to Disease is Their Greatest Weakness

However, medaka are highly susceptible to diseases like Aeromonas bacterial infections, which is their biggest drawback. Especially if you are also raising tropical fish like guppies, bacteria can spread from one tank to another, resulting in both tanks needing treatment.

Since medaka have small bodies, once they catch a disease, they can die within a few days.

In contrast, fish like goldfish and bettas infected with Aeromonas can survive for several months, which is why people perceive medaka as difficult to care for because they die so quickly.

Medaka Can Be Easily Raised with Medication

As a result, many people buy medaka only to see them fall ill and die quickly. I used to have a 100% mortality rate with the medaka I bought.

But after using Aguten and Elbagiu for treatment during the introduction phase, and treating them immediately upon noticing abnormalities, I now rarely lose medaka. This is unlike goldfish, which often don’t respond to medications at all, making medaka much easier to care for.

Medaka can be easily raised indoors if they receive proper treatment with medication. Once this is understood, the difficulty of raising medaka will decrease.

Other Fish That Are Easier to Raise

However, many fish are easier to care for than medaka.

For instance, guppies and platies, unless already infected when bought, don’t need treatment and won’t die easily. They are also very resistant to poor water quality.

Moreover, fish like White Cloud Mountain minnows, neon tetras, plecos, and African cichlids almost never get sick and can survive even in environments where other fish perish.

Saltwater fish, particularly damselfish, have much stronger vitality than freshwater fish. I’ve kept a clownfish without changing the water for three years. *Note that not changing water is standard in the saltwater fish world.

If you want to keep fish without much thought or care, it might be better to choose a fish that’s easier to care for than medaka.

Is Raising Medaka Difficult?

Medaka are prone to bacterial diseases like Columnaris, but they are resistant to poor water quality. Since they can be raised without heaters or filters, raising medaka itself isn’t difficult.

However, medaka are highly susceptible to pathogens from other tropical fish and goldfish and can suddenly die due to digestive problems if water changes are done immediately after feeding.

Especially just after introduction, there’s a risk of sudden death, so it’s best to acclimate them to the water and temperature slowly. If you’re also raising other fish (especially medaka-related ones like guppies), the chances of contracting strange diseases are high, so treating with Elbagiu or salt baths is effective.

Thus, while raising medaka isn’t inherently difficult, it isn’t extremely easy either because one mistake can lead to an entire tank dying.

Mysterious Sudden Deaths Also Occur

In particular, sudden deaths of seemingly healthy medaka are common among beginners. These deaths can occur due to various reasons, not just poor water quality, which is why even people who can keep other fish like tropicals and goldfish might find their medaka dying.

I’ve asked both amateur and professional breeders, and many of them experienced massive and sudden deaths when they first started keeping medaka.

However, if you keep raising medaka correctly for a while, the mass deaths will stop, so perseverance is key.

Medaka Are Easier or Harder to Raise Depending on Indoor vs. Outdoor Setup

Medaka have different care difficulties when raised indoors versus outdoors. They prefer sunlight, so raising them outdoors allows for almost complete neglect, making it harder to kill them.

However, when raised indoors, they are more susceptible to disease and their fry don’t grow well.

Otherwise, medaka are more tolerant of poor water quality than other fish and can be raised indoors with minimal water changes.

I also struggled with indoor care and lost many medaka, but by carefully monitoring diseases and properly acclimating them, I’ve had hardly any medaka deaths recently.

Given this, raising medaka outdoors isn’t difficult, but you might struggle indoors without understanding key care tips.

The Difficulty of Raising Medaka is Easy

I used to find the difficulty of raising medaka quite challenging, but now I believe it’s very easy. I would say it’s easier than raising Corydoras catfish and much easier than small Apistogramma species like rams.

However, medaka are susceptible to sudden death due to environmental changes during introduction, and once they decline, they rarely recover. Especially when raised in tanks, they can suddenly die or gradually decline.

Until I learned the tricks of caring for medaka, I also had a 100% mortality rate, but I’ve had almost no deaths after adopting proper care practices.

Therefore, raising medaka isn’t inherently difficult, but it’s not as simple as caring for guppies or White Cloud Mountain minnows.

Here, I’ll compare the easy and challenging aspects of raising medaka with guppies and other low-maintenance fish.

The Difficulty Level of Raising Medaka vs. Goldfish

The difficulty of raising medaka versus goldfish depends on the type. Comparing medaka with long-bodied goldfish like wakin or comets, goldfish are much easier. Goldfish don’t typically die right away or gradually waste away unless infected.

However, medaka can be wiped out unless introduced carefully, making them harder than long-bodied goldfish.

That said, round-bodied goldfish like ranchu are delicate, prone to disease, sudden death, and unexplained illness, making them harder than medaka. If you can handle delicate varieties like ranchu or ping-pong pearl, you’ll find raising medaka easy.

The Difficulty Level of Raising Medaka vs. Guppies

Compared to medaka, guppies are overwhelmingly easier to raise.

Guppies are highly tolerant of poor water quality. While medaka are endangered in the wild, guppies are thriving in Japanese rivers due to climate change. Guppies can thrive with loose feeding, water changes, and acclimation practices.

Additionally, guppy fry are born already grown, making them very resilient. Trying to raise medaka like guppies will almost certainly result in failure.

As mentioned, medaka aren’t that weak, but tropical fish like guppies are just too resilient, making medaka seem difficult by comparison.

The Difficulty Level of Raising Medaka vs. Neon Tetras and White Cloud Mountain Minnows

Medaka are much harder to raise than neon tetras and White Cloud Mountain minnows. Neon tetras almost never get sick. They’re incredibly resilient tropical fish and resistant to poor water quality. In contrast, raising medaka like neon tetras will likely result in total mortality.

The Difficulty Level of Raising Medaka vs. Bettas

Medaka and bettas have similar care difficulty. While bettas are said to be able to live in bottles, they aren’t particularly tolerant of poor water quality


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