Preciso aclimatar o peixe ornamental e verificar a oxigenação.

In Brazilian Portuguese, the subject pronoun is often omitted when the verb form already makes the subject clear.

• Preciso = I need
• The ending -o shows it is eu.

So:

• Preciso aclimatar o peixe ornamental... = I need to acclimate the ornamental fish...
• Eu preciso aclimatar o peixe ornamental... is also correct, but eu is often unnecessary unless you want emphasis or contrast.

For example:

• Eu preciso, mas ele não precisa. = I need to, but he doesn’t.

Because precisar can be followed directly by an infinitive when you mean need to do something.

Pattern:

• precisar + infinitive

Examples:

• Preciso sair. = I need to leave.
• Preciso estudar. = I need to study.
• Preciso verificar a oxigenação. = I need to check the oxygenation.

This is different from precisar de, which is used before a noun:

• Preciso de ajuda. = I need help.
• Preciso de um aquário maior. = I need a bigger aquarium.

So in your sentence:

• Preciso aclimatar... = I need to acclimate...

Aclimatar means to acclimate or to help something adjust to a new environment or condition.

In everyday speech, it is somewhat technical or semi-technical, but it is very natural in contexts like:

• fishkeeping
• animals
• plants
• temperature/environment adjustment

For example:

• aclimatar o peixe = to acclimate the fish
• aclimatar a planta = to acclimate the plant

In an aquarium context, it usually means helping the fish gradually adapt to the water conditions, temperature, and so on.

Portuguese often uses articles more than English does.

Here, o peixe ornamental can mean:

• the ornamental fish (a specific fish already known in the situation)

In context, this is very natural. If you are talking about a particular fish you have, the article makes sense.

You may also see bare nouns in some contexts, but Portuguese generally likes definite or indefinite articles more than English:

• o peixe = the fish
• um peixe = a fish

So o peixe ornamental sounds complete and natural.

In Portuguese, adjectives usually come after the noun.

So:

• peixe ornamental = ornamental fish
• água fria = cold water
• planta aquática = aquatic plant

This is one of the most common word-order differences from English.

Sometimes adjectives can come before the noun, but that often changes the tone or meaning. In this sentence, the normal order is:

• peixe ornamental

In this case, ornamental does not change between masculine and feminine singular.

Examples:

• o peixe ornamental
• a planta ornamental

But it does change in the plural:

• os peixes ornamentais
• as plantas ornamentais

So the singular form is ornamental, and the plural form is ornamentais.

E means and.

It connects the two actions that the speaker needs to do:

• aclimatar o peixe ornamental
• verificar a oxigenação

So the structure is:

• Preciso [fazer ação 1] e [fazer ação 2].

Examples:

• Preciso comprar comida e limpar o aquário.
• Preciso alimentar os peixes e trocar a água.

Because it is coordinated with aclimatar after preciso.

The sentence has this structure:

• Preciso + aclimatar + ... e verificar + ...

In English, this works the same way:

• I need to acclimate the fish and check the oxygenation.

Portuguese does not need to repeat preciso:

• Preciso aclimatar o peixe ornamental e verificar a oxigenação.

You could repeat it, but normally you would not:

• Preciso aclimatar o peixe ornamental e preciso verificar a oxigenação.

That version is grammatical, but less elegant unless you want emphasis.

This is an important vocabulary point.

• oxigênio = oxygen
• oxigenação = oxygenation, the process or level of oxygen being present

So:

• verificar o oxigênio could mean checking the oxygen itself, or the oxygen supply/amount, depending on context
• verificar a oxigenação means checking the oxygenation level or process, which is more natural in technical or aquarium-related language

In an aquarium context, oxigenação often refers to how well the water is oxygenated.

Yes. Oxigenação is feminine, so it takes the feminine article a.

Many Portuguese nouns ending in -ção are feminine:

• a oxigenação
• a informação
• a adaptação
• a verificação

So in the sentence:

• verificar a oxigenação

In Brazilian Portuguese, peixe is pronounced approximately like PAY-shi or PAY-shuh, depending on accent.

A rough guide:

• pei sounds like pay
• x here sounds like sh
• final e is often a light i-like sound in Brazilian Portuguese

So:

• peixe ≈ PAY-shi

Be careful: the x in Portuguese can have different sounds in different words, but in peixe it is the sh sound.

A rough Brazilian pronunciation is:

• o-xi-ge-na-ÇÃO
• approximately: o-zhee-zheh-nowng

The stressed syllable is the last one:

• ção

A few useful points:

• x in oxi sounds like sh in many Brazilian accents
• ge sounds like the s in measure or zh
• ção is a very common ending, with stress on that final syllable

If you want to sound more natural, focus especially on the stress:

• oxigenaÇÃO

No, that is not the normal Brazilian Portuguese structure.

In Brazilian Portuguese, when precisar is followed by a verb, you normally use:

• precisar + infinitive

So:

• Preciso aclimatar o peixe ornamental.

Not:

• Preciso de aclimatar...

Use de when a noun comes after precisar:

• Preciso de ajuda.
• Preciso de mais tempo.

Yes, but in this sentence it is clearly a verb, not an adjective.

There are two different words here:

• preciso (verb form of precisar) = I need
• preciso (adjective) = precise, accurate

Examples:

• Preciso verificar a oxigenação. = I need to check the oxygenation.
• O teste é preciso. = The test is precise.

So context tells you which meaning it has.

Yes, possibly, depending on tone.

• verificar = a bit more formal/neutral; very common and safe
• checar = common in Brazil, a bit more informal, from English check
• conferir = can mean check/verify, often used when confirming something

In an aquarium or care-related sentence, verificar sounds very natural:

• Preciso verificar a oxigenação.

Possible alternatives:

• Preciso checar a oxigenação.
• Preciso conferir a oxigenação.

All are understandable, but verificar is probably the most standard choice here.