Tinder reply when she opened by asking if I've been to the aquarium downtown lately

A question like this is almost always a way to start talking, not a test of your calendar. She picked something specific so you'd have something specific to respond to. The fact that she named a place downtown also tells you she's likely local, or at least has a reason to know the spot. You can read the question as a mild, low-pressure opener from someone who wants to see whether you're easy to talk to.

Check her profile before you answer. If she mentions the ocean, animals, a particular trip, or a hobby that connects to aquariums, the question probably came from something she saw in your profile or wants to explore. Match the energy of the question instead of overthinking it. If she sent it casually, a casual answer is correct.

The first kind is the honest answer with one detail. You confirm where you've been or haven't, then add a single true observation about the place: what you liked, what surprised you, or what you still want to see. The job is to give her a hook. She now has something she can ask about or agree with, and the conversation can move on from there.

The second kind is the answer that turns the question into a plan. You say you've been and then mention a thing you'd want to see again or a time you'd go, leaving room for her to join. This works when the chat already feels warm. It should stay light enough that she can say no without it being awkward. Leave out any specific date or pressure to meet. The third kind is the honest "not in ages" answer, followed by a question about what she's been up to or what got her thinking about it. This keeps things moving without bluffing, and it gives her an easy opening to share about herself. Avoid long replies, avoid asking her to justify her own question, and avoid anything that sounds like you're grading whether she knows the place well.

Answer the same day if you can, ideally within a few hours while the question is still fresh. A question about a place is time-sensitive in a small way: it reads as an invitation, and a long gap makes it feel like you weren't interested. If you're replying late at night, it's fine to send a short answer, but save anything that sounds like a plan for daytime when you can actually follow through.

If she doesn't reply within a day or two, send one short follow-up that adds a little new information or a light question, not a repeat of the first message. If that also goes unanswered, let it go. Two unanswered messages in a row is a clear signal, and sending a third makes you look more invested than the situation supports. Move on rather than chasing a thread that has stopped.