Ok so if you were going to ask me for an optimal age for this I would have a tough time answering that. I’ve spent a lot of time in Vancouver and I find the aquarium there is a much more educational and multi generational experience, with a wider range of activities to interest all kinds of ages. The Toronto aquarium, on the other hand, is a really neat, condensed, visual experience. From an educational standpoint you likely won’t get much for the preschoolers but I do think they will enjoy the experience. Tickets are $39 for adults and $13 for 3-5 year olds, under 3 get in free, and if you buy timed entry tickets ahead it’s $33 for adults and $10 for 3-5 year olds (kids 6-13 are $26 there and $23 if you buy ahead). So first tip; buy ahead.
Second tip; get there as close to opening as you can. We headed down aiming for a 9AM arrival (opening time) and missed by about 30mins due to traffic (and having toddlers), but it gave M some extra morning nap time in the car which was not terrible. This was a Saturday trip in the summer so peak timing for business, we spent about 2 hours there (a little under), and by the end it was busy but not terrible.
The path through the exhibits is pretty easy to follow but it is quite dark in a lot of areas so it definitely helps to have an adult for each kid and/or a carrier for one, especially if your little is a runner! The route starts with Canadian waters which was a nice opportunity to talk about fish we might have in bodies of water around us and in places she’s been and then transitioned to a lot of large scale tanks with an impressive array of fish and it was immediately interesting to V.

The entire area is quite stroller friendly which is a nice bonus, but I think you’d likely have a hard time keeping them in it – depends on the kid though! Once M saw V up and exploring I couldn’t have wrangled him back in even with two people. The rainbow reef had a lot of the fish types we had discussed in our prep work before the aquarium so great opportunities for getting her to point out which ones she recognized and she was fascinated to see how differently they moved. As usual, her favourite part was getting to point out what she knew to M.

M was interested in the visuals but not too engaged in listening to what he was looking it, unsurprisingly. This did offer lots of opportunity for different types of movement – there are areas with crawling tunnels and lights on the floor that made for a happy crawler if you don’t mind a bit of dirt (don’t forget the wipes!). There is also an excellent chance someone will want to lick the glass. Not speaking from experience, of course.

Next up was the shark area, which involves a moving sidewalk through an aquarium tunnel with sharks and other marine life swimming overhead. Super cool for both adults and kids but a bit tricky for early walkers so you’ll want to keep an eye out for that. It’s quite slow moving so not too much concern there but can be tricky to transition between the moving/not moving area so it takes a minute for the littles to get used to. Shark spotting was really fun for everyone and V loved seeing them in person and even recognized differences between some of them from her model sharks we used in her sensory bin.

The jellyfish zone is really interesting to look at and gave a great crawl zone for M but it is quite dark and was definitely a little trickier keeping both of them close while they were excited seeing the lit jellies. The area with the rays caught both kids’ attention for quite a while, I think the way they swam so differently was a big draw. Personally, I also liked that some of them seemed quite smiley.

There’s also a touch area which provided some interest for V and endless frustration for M who wanted nothing more than to go in for a dip. Definitely not designed for the teeniest visitors (for good reason, you do need to be gentle while touching so this is definitely a know you kid moment, if it’s too much this is a good one to skip past)

The last hurdle was that there is a quite large play area near the end with a two story slide area. This gets quite busy and it’s pretty tough to follow your little up as an adult so unless they are quite good at following instructions or you have an older kid with you to help supervise this may be a trouble zone. Nearby there are some cool see through tunnels with fish underneath and a pretend submarine area to explore that are more toddler and parent friendly. Also fair warning you will be forced to walk through the gift shop at the exit so you may want to prepare your little ahead of time for how you plan to deal with that. V was pretty tired at that point and content to be reminded she had many fish friends at home to play with.
A final note is that we went for lunch on a patio at the Delta hotel very nearby, at Bremner and Lower Simcoe, a very short walk away. Normally I wouldn’t necessarily review a restaurant but the staff at the patio were so incredibly nice – they let us sit out even though it wasn’t open yet while they were preparing the patio for service, the meals had good vegetable and kid options, and at the end when M dropped his teether on the floor they took it away and sterilized it for us. So incredibly kind and makes a huge difference when you’re out with toddlers. A little pricier than we would normally do but definitely worth it given the service.