The cheapest aquariums come from big-box retailers and online marketplaces, not specialty pet stores
The lowest prices on aquariums are at Walmart, Target, Amazon, and Petco during their sales cycles. A 10-gallon tank costs $15 to $25 at these retailers, while the same tank at a local aquarium shop runs $30 to $50. Online marketplaces like eBay and Facebook Marketplace also carry used tanks—often in good condition—for $5 to $15. The trade-off is selection: big-box stores stock only the most common sizes (10, 20, 29, and 55 gallons), while specialty shops carry unusual dimensions and higher-end glass.
Price varies by season. Summer is peak buying season, so prices stay high June through August. Fall and winter see deeper discounts, especially in September and January when retailers clear inventory. Black Friday and Cyber Monday (late November) typically offer 20 to 40 percent off tanks and kits. Checking prices across three or four retailers before buying saves $10 to $30 on a single tank.
Key Takeaways
- Walmart, Target, and Amazon consistently undercut specialty pet stores by $15 to $25 per tank.
- Used aquariums on Facebook Marketplace and Craigslist cost half the retail price and are often structurally sound if the glass is clear and the seams are intact.
- Buying in fall or winter, or waiting for holiday sales, can cut the price by 20 to 40 percent compared to summer prices.
- A 10-gallon starter kit (tank, filter, heater, light) costs $40 to $80 at big-box stores versus $100 to $150 at specialty shops.
Used tanks from online marketplaces and local sellers
Facebook Marketplace, Craigslist, and OfferUp list used aquariums constantly. Prices run $5 to $20 for a 10-gallon tank and $20 to $50 for a 20-gallon, depending on condition and your region. Before buying, inspect the glass for cracks, cloudiness, or white mineral buildup that signals hard water damage. Check the seams—the silicone seal where glass panes meet—for gaps or discoloration, which means the tank may leak.
Ask the seller how long they owned it, whether it held water without leaking, and why they are selling. A tank used for two years and drained properly is safer than one sitting in a garage for five years. Request photos of the inside and seams before you travel. Many sellers will hold a tank for 24 hours if you commit to picking it up.
Bring a flashlight and a level when you inspect in person. Fill the tank with water in the seller's driveway (or ask permission to do so) and watch for leaks for five minutes. A slow drip from a seam means the tank is not worth the risk, even at a low price. If it holds water and the glass is clear, you have found a deal.
Starter kits versus buying components separately
A starter kit bundles a tank, filter, heater, light, and sometimes a stand into one box. Kits at Petco, Walmart, and Amazon cost $40 to $80 for a 10-gallon setup. Buying each piece separately—a $20 tank, $15 filter, $12 heater, $10 light—totals $57 to $70, so kits save money only if the filter and heater are decent quality.
Read reviews before buying a kit. Many budget kits include weak filters that cannot handle a full tank of water or heaters that fail within months. A $50 kit with a poor filter may cost more in the long run than a $25 tank plus a $20 reliable filter. Check the filter's flow rate (measured in gallons per hour, or GPH) against the tank size—it should be at least three times the tank volume per hour. A 10-gallon tank needs a filter rated for 30 GPH or higher.
If the kit's filter or heater has poor reviews, buy the tank from the kit and replace those components with standalone units. This hybrid approach often costs the same as the full kit but gives you better equipment.
Seasonal sales and when to buy
Petco and PetSmart run sales tied to holidays and inventory cycles. Memorial Day (late May) and Labor Day (early September) bring 15 to 25 percent discounts on tanks and kits. Black Friday (late November) and Cyber Monday offer the deepest cuts—often 30 to 40 percent off. January sales clear holiday inventory, and prices drop again in late August before the back-to-school season ends.
Sign up for email alerts from Petco, PetSmart, Walmart, and Target. They announce sales three to five days before they start, giving you time to compare prices. Check the sale price against the regular price—some retailers inflate the regular price before marking it down, so the "sale" price is still higher than the everyday price elsewhere.
Amazon Prime Day (mid-July) and Prime Early Access Sale (mid-October) offer discounts on aquariums and kits if you have a Prime membership. Non-members can still see the deals but do not get the discount. If you plan to buy in July or October, a Prime membership ($139 per year or $14.99 per month) pays for itself if you use it for other purchases.
Comparing tank sizes and what each costs
| Tank Size | Big-Box Retail | Specialty Shop | Used (Average) |
|---|---|---|---|
| 10 gallons | $15–$25 | $30–$50 | $5–$15 |
| 20 gallons (long) | $25–$40 | $50–$75 | $15–$30 |
| 29 gallons | $35–$55 | $70–$100 | $20–$40 |
| 55 gallons | $50–$80 | $120–$180 | $30–$60 |
The 10-gallon tank is the cheapest entry point and costs $15 to $25 new at Walmart or Target. It is small enough to fit on a desk or shelf but large enough for a few small fish or a betta. A 20-gallon long tank (30 inches wide, 12 inches deep) costs $25 to $40 and holds more fish with less height, making it easier to maintain.
Larger tanks (29 and 55 gallons) cost more upfront but are cheaper per gallon of water. A 55-gallon tank at Walmart costs $50 to $80, or about $0.91 per gallon. A 10-gallon tank costs $15 to $25, or $1.50 to $2.50 per gallon. If you plan to keep fish long-term, a larger tank is a better value—and fish thrive in more space.
What to avoid when shopping for cheap aquariums
Avoid tanks with visible cracks, cloudiness, or white scaling inside the glass. Cloudiness from mineral deposits can sometimes be cleaned, but cracks mean the tank will leak. Do not buy a tank without a stand unless you already own one—a stand costs $30 to $100 new, and a cheap tank plus a new stand erases your savings.
Avoid "all-in-one" kits with built-in filters and lights if reviews mention the filter failing or the light burning out quickly. These integrated systems are hard to repair or replace. A modular setup—separate tank, filter, heater, and light—costs the same or less and lets you swap out broken parts without replacing the whole unit.
Do not buy a tank based on price alone if the seams look weak or the glass feels thin. A $10 tank that leaks after two weeks costs more than a $25 tank that lasts five years. Inspect used tanks in person before handing over money, and ask the seller for a brief window to test it at home (usually 24 to 48 hours) before committing.
Frequently Asked Questions
Is it safe to buy a used aquarium?
Yes, if the glass is clear, the seams are intact, and it holds water without leaking. Test it by filling it with water for five minutes before you take it home. Aquarium glass does not degrade over time if it was not cracked or exposed to extreme temperature changes. A 10-year-old tank in good condition is as safe as a new one.
What is the difference between a 10-gallon and a 20-gallon tank?
A 10-gallon tank is smaller and cheaper ($15–$25) but holds fewer fish and requires more frequent water changes. A 20-gallon tank costs $25–$40 and gives fish more room, making the water chemistry more stable. For a beginner, a 20-gallon is worth the extra $10–$15 because it is easier to maintain.
Should I buy a kit or build my own setup?
A kit saves money if the filter and heater have good reviews. If they do not, buy the tank from the kit and replace the filter and heater with standalone units. Check the filter's flow rate and the heater's wattage against your tank size before buying.
When is the best time to buy an aquarium?
Fall and winter (September through January) have the lowest prices. Black Friday and Cyber Monday offer 30–40 percent discounts. If you can wait, buying in September or January saves $10–$30 compared to summer prices.
Can I use a cracked aquarium if I seal it?
No. Silicone sealant is not designed to hold water pressure from inside a tank. A crack will grow under pressure and eventually fail, flooding your floor. A cracked tank is not worth the risk, even if the price is very low.