Welcome to Under the Sea
Aquatics
We’re a family-owned aquarium shop in St. Catharines. From premium tanks and filters to live plants and healthy fish, we help you build a beautiful, low-stress aquarium—plus guidance on setup, water care, and stocking that works.
- Water testing & honest advice
- Starter kits to custom builds
- Live plants, hardscape & décor
- Setup, aquascaping & maintenance
Popular Categories
Marine
Freshwater
Our awsome services section
Reef & Saltwater
Corals, fish, and gear—We set up, cycle, and tune your reef for stable, vibrant growth.
Healthy Fish
Carefully sourced and observed so you take home stress-free fish.
Plants & Rock
Fresh plants, driftwood, and stones—hand-picked and easy to keep.
Maintenance
Scheduled water changes, glass clean, and filter care.
Featured Arrivals
Expertise You Can Trust
With over 25+ years of experience, our marine biologists ensure every animal is healthy, quarantined, and ready for its new home.
What Our Customers Are Saying!
Absolutely the healthiest fish I’ve ever received. The team was incredibly knowledgeable and helped me pick the perfect tank mates. Highly recommend!
Sarah K. Reef Hobbyist 
As a beginner, I was lost. The staff at Under the Sea walked me through every step, from water testing to setup. My tank is beautiful and stable, all thanks to them.
Mike T.New Aquarist
Amazing selection of hardscape and plants. I found rare pieces here I couldn't get anywhere else. My go-to shop for all my aquascaping needs.
Jenny L.Aquascaper