Аквариумный фильтр и биофильтр работают с аквариумным компрессором.

Because the subject is actually two things joined by и:

• аквариумный фильтр
• биофильтр

Together they form a plural subject, so the verb must also be plural:

• работают = work / operate

If there were only one subject, you would use singular:

• Аквариумный фильтр работает... = The aquarium filter works...

They are in the nominative case because they are the subjects of the sentence — the things doing the action.

So:

• аквариумный фильтр
• биофильтр

are both the ones that работают.

In Russian, the subject of a sentence is normally in the nominative case.

Because the preposition с in the meaning with / together with / using usually requires the instrumental case.

So:

• компрессор → компрессором
• аквариумный → аквариумным

That is why you get:

• с аквариумным компрессором

This means something like with an aquarium compressor or using an aquarium compressor.

Here с means with in the sense of in combination with or using.

So работают с аквариумным компрессором means that the filter and biofilter operate together with, or are powered/aided by, an aquarium compressor.

It does not mean simple physical location like near or at. It describes how they function.

Because it modifies two different nouns:

• аквариумный фильтр
• аквариумным компрессором

In English, we might sometimes avoid repetition if the meaning is obvious, but in Russian it is completely normal to repeat the adjective when it belongs to each noun separately.

Also, the adjective has to match each noun in:

• gender
• number
• case

So the forms are different here:

• аквариумный фильтр — masculine, nominative singular
• с аквариумным компрессором — masculine, instrumental singular

Аквариумный means aquarium as an adjective: aquarium filter, aquarium compressor, etc.

It is formed from the noun аквариум (aquarium) plus the adjective ending -ный.

So:

• аквариум = aquarium
• аквариумный = aquarium-related / for an aquarium

Russian often uses adjectives where English may use a noun in front of another noun.

For example:

• аквариумный фильтр literally = aquarium-related filter
• natural English = aquarium filter

Grammatically, both are masculine singular nouns in the nominative case here.

The difference is mainly lexical:

• фильтр = filter
• биофильтр = biofilter

The word биофильтр is a compound word:

• био- = bio-
• фильтр = filter

In this sentence, both nouns behave normally and are coordinated with и.

Yes. Russian word order is fairly flexible.

The neutral order here is:

• Аквариумный фильтр и биофильтр работают с аквариумным компрессором.

But other orders are possible, depending on emphasis. For example:

• С аквариумным компрессором работают аквариумный фильтр и биофильтр.

This could emphasize with an aquarium compressor first.

Even when the order changes, the case endings still show the grammatical roles, so the meaning usually stays clear.

Russian has no articles like the or a/an.

So:

• Аквариумный фильтр can mean an aquarium filter or the aquarium filter
• аквариумным компрессором can mean an aquarium compressor or the aquarium compressor

The exact meaning depends on context.

This is very normal in Russian, and learners usually have to get used to understanding definiteness from the situation rather than from an article.

Yes, very often.

Работать с commonly means:

• to work with
• to operate with
• to function with
• to use together with

In this technical sentence, работают с аквариумным компрессором is best understood as operate with or work together with an aquarium compressor.

So this is a normal and useful pattern to learn:

• работать с + instrumental

The ending -ом is a very common instrumental singular ending for masculine and neuter nouns after many hard stems.

So:

• компрессор → компрессором

The adjective changes too:

• аквариумный → аквариумным

Together they show the whole phrase is in the instrumental case:

• с аквариумным компрессором

This is a good pattern to remember:

• masculine adjective in instrumental singular: -ым / -им
• masculine noun in instrumental singular: often -ом / -ем

A helpful stress guide is:

• аквариу́мный
• фи́льтр
• биофи́льтр
• рабо́тают
• с аквариу́мным компре́ссором

So the whole sentence is approximately:

• аквариу́мный фи́льтр и биофи́льтр рабо́тают с аквариу́мным компре́ссором

Pay special attention to:

• рабо́тают — stress on бо
• компре́ссором — stress on пре
• аквариу́мный — stress on у́

Sometimes yes, but not in exactly the same way English might.

For example, if the context is already clear, Russian could shorten things in conversation. But in a clean, technical sentence like this, repeating the full terms is natural and clear:

• аквариумный фильтр и биофильтр
• с аквариумным компрессором

Russian often prefers clarity, especially in factual or technical statements. So this sentence sounds normal as written.