Akwarium stoi w salonie przy oknie, bo mała rybka lubi światło.

In Polish, stać / stoi is very commonly used for objects that are upright and placed somewhere.

So:

• Akwarium stoi... = The aquarium is standing...
• Natural English translation: The aquarium is in the living room...

Polish often distinguishes between:

• stoi = stands upright
• leży = lies horizontally
• wisi = hangs
• jest = is

So stoi sounds more natural than jest here, because an aquarium is seen as a physical object placed somewhere.

Because the preposition w meaning in takes the locative case when it describes location.

• basic form: salon = living room
• locative after w: w salonie = in the living room

This is a very common pattern:

• w domu = in the house
• w pokoju = in the room
• w sklepie = in the shop
• w salonie = in the living room

So w salonie is required by grammar.

The preposition przy means something like by, next to, or near, and it also requires the locative case.

• basic form: okno = window
• locative: oknie
• so: przy oknie = by the window / near the window

This is another fixed preposition + case combination that you simply learn together:

• przy stole = at the table
• przy drzwiach = by the door
• przy oknie = by the window

It can be translated in several similar ways depending on context:

• by the window
• near the window
• sometimes at the window

In this sentence, by the window is probably the most natural English choice.

Przy usually suggests something is close to another thing, not necessarily directly touching it.

Because in Polish, bo introduces a subordinate clause meaning because, and it is normally preceded by a comma.

So:

• Akwarium stoi w salonie przy oknie, bo mała rybka lubi światło.

This is standard Polish punctuation.

In English, we may or may not use a comma before because, depending on style and meaning. In Polish, the comma here is expected.

Bo means because.

It is very common in everyday speech and writing.
Ponieważ also means because, but it sounds a bit more formal or neutral.

So:

• bo = because, common and natural
• ponieważ = because, slightly more formal

In this sentence, bo sounds perfectly normal.

Rybka is a diminutive form of ryba.

• ryba = fish
• rybka = little fish / fishy / small fish

Here mała rybka literally means small little fish, though in natural English you would probably just say the little fish or the small fish.

Using a diminutive in Polish can express:

• small size
• affection
• friendliness
• a cute tone

So rybka sounds softer and sweeter than ryba.

Because Polish often combines a diminutive noun with an adjective for extra emphasis or a more affectionate tone.

So mała rybka is not wrong or redundant in an unnatural way. It can sound:

• cute
• gentle
• expressive

It emphasizes that the fish is small.

A similar idea in English would be something like:

• the little fish
• the tiny fish

Even though rybka already has a diminutive sense, adding mała is still very natural.

It is in the nominative singular, because it is the subject of the second clause:

• mała rybka lubi światło = the little fish likes light

Breakdown:

• mała = feminine singular nominative adjective
• rybka = feminine singular nominative noun

They match because adjectives in Polish agree with the noun in:

• gender
• number
• case

Since rybka is feminine singular nominative, mała must be too.

The verb lubić takes the accusative case for its direct object.

So we ask: what does the little fish like?
Answer: światło.

Now the important detail: światło is a neuter noun, and in the singular, many neuter nouns have the same form in the nominative and accusative.

So:

• nominative: światło
• accusative: światło

That is why the form does not change, even though grammatically it is accusative here.

It can mean either, depending on context.

Polish has no articles like a or the, so światło could be understood as:

• light
• the light

In this sentence, English would most naturally say:

• the little fish likes light or
• the little fish likes the light

Both are possible depending on the exact context.

Polish word order is more flexible than English word order, because case endings show the grammatical roles.

The given sentence is natural and neutral:

• Akwarium stoi w salonie przy oknie, bo mała rybka lubi światło.

But some parts could be rearranged for emphasis, for example:

• W salonie przy oknie stoi akwarium...
• Przy oknie w salonie stoi akwarium...

These all still mean roughly the same thing, but the focus changes slightly.

The original version is straightforward and easy for a learner to follow.

Yes, you could, and it would be grammatically correct.

But the nuance is different:

• jest = is located / is
• stoi = stands

Jest is more general.
Stoi is more specific and often more natural for furniture, containers, bottles, vases, aquariums, and similar objects that are placed upright somewhere.

So:

• Akwarium jest w salonie... = The aquarium is in the living room...
• Akwarium stoi w salonie... = The aquarium stands / is standing in the living room...

In many contexts, stoi sounds more vivid and idiomatic.

A rough English-style pronunciation guide would be:

ah-KVAH-ryoom STO-yee v sah-LO-nyeh pshee OCK-nyeh, boh MAH-wah RIB-kah LOO-bee SHVYAH-twoh

A few useful pronunciation notes:

• w is pronounced like English v
• ł is pronounced like English w
• y is a separate vowel sound, not the same as English ee
• ś / si before a vowel gives a soft sh-like sound
• przy begins with a difficult cluster for English speakers; it sounds roughly like pshih or pszhih
• stoi is two syllables: sto-i, not one syllable

In Polish, salon usually means living room or lounge in a home.

In English, salon usually means a business like a:

• hair salon
• beauty salon

So this is a false friend to watch out for.

In this sentence:

• w salonie = in the living room

not in the salon in the usual English sense.