Аквариумный фильтр уже работает.

Russian often uses an adjective + noun structure where English uses noun + noun.

So:

• аквариумный фильтр = aquarium filter
• literally, aquarium-related filter

This pattern is very common in Russian. A few similar examples:

• кухонный стол = kitchen table
• зубная щётка = toothbrush
• зимняя куртка = winter jacket

So аквариумный describes what kind of filter it is.

They are in the nominative singular.

That is because фильтр is the subject of the sentence: it is the thing that works / is working.

• фильтр is a masculine singular noun
• аквариумный is a masculine singular adjective agreeing with it

So the forms match:

• аквариумный — masculine singular nominative
• фильтр — masculine singular nominative

The ending -ый is a common adjective ending for the masculine singular nominative form.

Because фильтр is:

• masculine
• singular
• nominative

the adjective must match it:

• аквариумный фильтр

If the noun changed, the adjective would change too. For example:

• аквариумная помпа — feminine
• аквариумное оборудование — neuter
• аквариумные растения — plural

This is called adjective agreement.

In Russian, the verb to be is usually omitted in the present tense.

So where English says:

• The aquarium filter is already working

Russian simply says:

• Аквариумный фильтр уже работает

There is no separate present-tense word equivalent to is here. This is completely normal Russian grammar.

Уже means already.

In this sentence, it shows that the filter has reached that state by now. The idea is something like:

• it is already working
• it has started working by this point
• it is now functioning

So уже adds a sense of earlier than expected, by this time, or now in effect.

Работает is the 3rd person singular present tense form of работать.

Breakdown:

• dictionary form: работать
• present tense, 3rd person singular: работает
• subject: фильтр = it

So it means:

• works
• is working
• is operating

depending on context.

In Russian, работать is used both for:

1. people working
2. machines/devices functioning

So for a device, работает means:

• it works
• it is working
• it is operating
• it is functioning

That is very natural Russian.

For example:

• Компьютер работает. = The computer is working.
• Телефон не работает. = The phone doesn’t work.
• Фильтр работает. = The filter is operating.

Good question. Работает is from the imperfective verb работать, and that is natural here because the sentence describes the filter’s current functioning state.

• уже работает = it is already working / it is already in operation

Russian uses the imperfective present for an action or state that is currently happening.

If you wanted to focus on the moment it started working, you might use a different verb, for example:

• Фильтр уже заработал.

That means something closer to:

• the filter has already started working

So:

• уже работает = it is already functioning now
• уже заработал = it has already begun to function

The sentence as written is very natural:

• Аквариумный фильтр уже работает.

But Russian word order is more flexible than English. You can move words around for emphasis.

For example:

• Фильтр уже работает. — more neutral if the type of filter is already known
• Уже работает аквариумный фильтр. — more emphasis on already
• Аквариумный фильтр работает уже. — possible, but less neutral in many contexts

So yes, word order can change, but the original sentence is the most straightforward and standard.

Russian has no articles.

So фильтр can mean:

• a filter
• the filter

The context tells you which one is meant.

That means Аквариумный фильтр уже работает could correspond to English as:

• The aquarium filter is already working
• An aquarium filter is already working

In real use, the situation usually makes it clear which interpretation is intended.

The stress pattern is:

• аква́риумный
• фи́льтр
• уже́
• рабо́тает

A rough English-style pronunciation guide would be:

• ak-VA-ree-oom-ny
• FEEL-tr
• oo-ZHE
• ra-BO-ta-yet

So the whole sentence is roughly:

ak-VA-ree-oom-ny FEEL-tr oo-ZHE ra-BO-ta-yet

Not exact, of course, but it can help you get started.