#2 | Are you only raising fish in your tank? The hidden side of medaka keeping they don't teach you in elementary school

Last time, I introduced a case where a thorough cleaning, done with good intentions, led to the death of goldfish.

I will organize the cause of this not from the abstract perspective of the stress fish experience, but from the point of view of how substances within the aquarium move.

The primary source of nutrients in an aquarium is fish food.

While food supports the growth of medaka, it also produces waste and leftovers.

In the process of being broken down by microorganisms, these generate ammonia $${NH_3}$$, which is highly toxic to medaka.

To maintain a stable environment, a mechanism is needed to quickly process this ammonia $${NH_3}$$ and reduce its toxicity.

Therefore, we use nitrifying bacteria to convert it into nitrite $${NO_2^-}$$, and then into nitrate $${NO_3^-}$$.

The chemical formulas are as follows.

▶ (Stage 1) From ammonia to nitrite:
A reaction by ammonia-oxidizing bacteria (such as Nitrosomonas).
$${2NH_3 + 3O_2 \longrightarrow 2NO_2^- + 2H^+ + 2H_2O}$$

※ The $${H^+}$$ (hydrogen ions) released during this reaction are a factor that lowers the $${pH}$$ of the aquarium water. In other words, the water gradually becomes acidic.

▶ (Stage 2) From nitrite to nitrate:
A reaction by nitrite-oxidizing bacteria (such as Nitrobacter).
$${2NO_2^- + O_2 \longrightarrow 2NO_3^-}$$

As you can see from this chemical formula, oxygen $${O_2}$$ in the water is essential for this reaction, and purification proceeds when there is sufficient oxygen.

The finally produced $${NO_3^-}$$ is absorbed as nutrients by algae and aquatic plants. However, in many cases, they cannot absorb it all, so it gradually accumulates in the water.

The toxicity of $${NO_3^-}$$ is weak. Even so, if it accumulates too much, it has a negative impact on fish, so it is physically discharged outside the tank by periodically changing the water.

There is one point of caution here.

That is the difference in the speed at which bacteria multiply.

1. Decomposition bacteria (the side that creates ammonia):
Generally multiply explosively in a few hours to a few days, generating $${NH_3}$$

2. Nitrifying bacteria (the side that eliminates ammonia):
Require several weeks to a month to become established

Due to this time lag, the act of thorough cleaning was eliminating the slow-multiplying nitrifying bacteria and intentionally creating an environment where ammonia easily accumulates.

Next time, based on this mechanism, I'd like to compare the management patterns mentioned in #1!

🔗 Continues to the next article

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• Mathematical theme: #Aquarium #FishTank

• Subject: #Bacteria #NitrogenCycle #NitrogenCirculation #BiologicalFiltration #Biofiltration

• Usage scenario: #IndependentResearch #Relearning #Relearning #ClassroomIdeas

• Topic: #ILoveBiology #ILoveInquiryBasedLearning