Setting up a fish tank requires six non-negotiable items: a tank, a filter, a heater (for tropical fish), a thermometer, a water conditioner, and a test kit. Everything else is either optional or becomes necessary based on the specific fish and plants you want to keep. The good news is that a basic functional setup is not expensive. A 20-gallon starter setup with quality equipment runs $100 to $200 all-in, not counting the fish.

This guide covers everything you'll need, broken out by what's essential from day one and what you add as your setup grows. I'll give specific product recommendations with price ranges, explain what each item does, and point out where beginners typically spend money on things they don't actually need.

The Tank Itself

Start here. Tank size affects everything else: cost, stocking options, maintenance frequency, and how stable the water chemistry is.

Choosing a Tank Size

Bigger tanks are more forgiving for beginners. A 20-gallon tank is my standard recommendation for first-time fish keepers. It holds enough water volume that chemistry changes slowly, giving you more time to respond to problems. A 5-gallon tank can swing from healthy to dangerous water chemistry within hours when something goes wrong, which makes it harder to keep fish alive when learning.

  • 5 to 10 gallons: Best for betta fish or small shrimp. Less forgiving of mistakes.
  • 20 to 29 gallons: Great starter size. Works for most community fish species.
  • 40 to 55 gallons: Excellent for a diverse community or a single larger species like cichlids.

Tank vs. Starter Kits

All-in-one starter kits like the Aqueon Aquarium Starter Kit 20 Gallon or the Fluval Flex 32.5 Gallon bundle the tank, filter, light, and sometimes a heater together at a lower combined price than buying separately. The quality of the included equipment varies. Fluval's bundled equipment is genuinely good. Many cheaper kit filters are undersized for the tank they come with. Research the included filter rating before buying a kit.

Filter

A filter is not optional. It houses the beneficial bacteria that convert toxic ammonia (from fish waste and uneaten food) into less harmful nitrate, and it removes physical debris from the water.

Types of Filters

Hang-on-Back (HOB) Filters: The most common type for tanks up to 75 gallons. The Aquaclear 20 (for 20-gallon tanks), Aquaclear 30, and Aquaclear 50 are among the best HOB filters available at $25 to $45. The Seachem Tidal 35 is another excellent option with a surface skimmer and adjustable flow.

Canister Filters: External filters that sit under the tank and offer more filtration volume. The Fluval 207 is ideal for 30 to 45-gallon tanks ($80 to $100), and the Fluval 307 handles up to 70 gallons. Better for larger setups and planted tanks.

Sponge Filters: Air-driven filters that are gentle and inexpensive. The Hikari Bacto-Surge Foam Filter and the XY-2831 sponge filters are popular for shrimp tanks, fry rearing, or as supplemental filtration in community tanks. They run on a standard air pump and cost $5 to $15.

Filter Sizing

A common guideline is to filter the tank's entire volume 4 to 6 times per hour. For a 20-gallon tank, a filter rated at 80 to 120 GPH is appropriate. More turnover is generally better for fish health, with the exception of tanks with slow-water fish like betta fish, where excess flow stresses them.

Heater

Most tropical freshwater fish need water between 72 and 80 degrees Fahrenheit. Room temperature is typically 68 to 72 degrees in most homes, which is too cold for most tropical species.

Heater Wattage

A rough guideline is 5 watts per gallon of water for standard room temperatures. A 20-gallon tank needs a 100-watt heater. In a cool room (below 65 degrees F), use the next step up. The Aqueon Pro 50W, 100W, and 150W heaters are reliable and include automatic shut-off protection. The Eheim Jager 100W is my recommendation for tanks 30 gallons and up. It has an accurate adjustable thermostat calibrated to 0.5 degrees Celsius.

Heater Guards

Heater guards are plastic cages that prevent fish from resting directly against the heater glass and burning themselves. Pleco fish, large cichlids, and clumsy fish are prone to this. They cost $3 to $8 and are worth adding if you keep bottom-dwelling or slow-moving fish.

Thermometer

A heater's internal thermostat can drift. A separate thermometer tells you what the water temperature actually is, not what the heater thinks it is.

The Marina Floating Thermometer ($3 to $5) is accurate and doesn't require batteries. The Zacro LCD Digital Aquarium Thermometer ($7 to $10) reads instantly and displays to one decimal place. Either works fine. I use a digital one because the one-second read time is convenient during water changes.

Lighting

Fish need light, and plants need it even more. The appropriate light depends on whether you're keeping a planted tank or a fish-only setup.

Fish-Only Lighting

Any full-spectrum LED strip or hood light gives the right balance of visible light without promoting excessive algae. Most HOB filter kits include a basic LED light. The Nicrew ClassicLED is a popular aftermarket upgrade at $20 to $35 for a 24 to 30-inch fixture.

Planted Tank Lighting

Plants need higher light intensity and a spectrum that promotes photosynthesis (peaking around 6500K to 7000K color temperature). The Fluval Plant 3.0, Finnex Planted+ 24/7, and the Chihiros WRGB II are well-regarded planted tank lights in the $50 to $200 range depending on size.

For a look at products available from online aquarium retailers, the Best Online Fish Supply Store guide covers where to find competitive pricing and good selection.

Water Conditioner

Tap water contains chlorine or chloramine at levels that kill fish. Water conditioner neutralizes these before the water enters the tank.

Seachem Prime is the best option for most hobbyists. It's the most concentrated conditioner available (5 mL treats 50 gallons), also temporarily detoxifies ammonia and nitrite, and one 100 mL bottle treats thousands of gallons. Cost is around $6 to $10 for 100 mL. API Stress Coat is another option that adds aloe for slime coat support.

Water Test Kit

You cannot see water chemistry problems. A test kit is how you know the nitrogen cycle is established and whether your water parameters are safe for fish.

API Freshwater Master Test Kit ($22 to $30) tests ammonia, nitrite, nitrate, and pH using liquid reagents. This is the standard recommendation. It contains enough reagent for hundreds of tests and comes with a color comparison card. Strip tests (like Tetra EasyStrips) are faster but less accurate and should not be relied on for critical readings.

Substrate

Substrate covers the bottom of the tank. It's required for most setups, though bare-bottom tanks are used by breeders and cichlid keepers who prefer easier cleaning.

  • Gravel: Standard aquarium gravel in 2 to 5mm size is inert and easy to clean. CaribSea Super Naturals aquarium gravel is a popular choice at $15 to $25 per 20-pound bag.
  • Sand: Preferred by fish that sift substrate like corydoras, loaches, and some cichlids. Carib Sea Aqua Natural White Sand or similar fine-grain sands work well. $15 to $25 per 20 pounds.
  • Planted substrate: If you want to grow plants, a nutrient-rich substrate like Fluval Stratum or CaribSea Eco-Complete provides iron and minerals plants use. $20 to $30 per bag.

Air Pump and Airstones (Optional but Useful)

An air pump isn't required if your filter creates adequate surface agitation, but it adds visible movement to the tank and can be helpful in warmer months when dissolved oxygen decreases.

The Tetra Whisper 10 handles tanks up to 10 gallons quietly for around $7. The Fluval Q5 handles up to 50 gallons. Pair with a standard airstone (under $2) or a rigid bubble wall wand for different visual effects.

Gravel Vacuum

A gravel siphon for water changes is an essential maintenance tool, even if it's not needed at initial setup.

The Python Pro-Clean Gravel Washer and the Lee's Ultimate Gravel Vacuum are the most reliable options. For a 20-gallon tank, the medium size works well and costs $10 to $15.

For more details on aeration equipment and oxygenation options, including how to size an air pump for your tank, see the Oxygen Machine for Fish Tank Price guide.

FAQ

What do you need to set up a fish tank for beginners? The must-haves for a basic setup are: tank, filter, heater (for tropical fish), thermometer, water conditioner, substrate, and a test kit. A light is needed for anything beyond a temporary setup. With these seven items, you can cycle the tank, establish water chemistry, and keep fish safely. Everything else is an upgrade or specialty item.

How long does it take to cycle a new fish tank before adding fish? The nitrogen cycle, where beneficial bacteria establish and start converting ammonia to nitrite to nitrate, takes 4 to 6 weeks in a new tank. You can speed this up by adding established filter media from another tank, using bacterial supplements like Tetra SafeStart Plus or Dr. Tim's Aquatics One and Only, and adding an ammonia source (a small pinch of fish food daily works). Test daily during cycling. Fish can be added when ammonia and nitrite both read zero and nitrate is present.

Do you need a filter for a fish tank? Yes. Without a filter, ammonia from fish waste accumulates rapidly and kills fish. Even in very small setups, some form of filtration is needed. The only exception is heavily planted tanks where plants outcompete bacteria for nutrients, but even these benefit from at least gentle circulation. A simple sponge filter running on an air pump is the minimum workable solution.

How much does it cost to set up a 20-gallon fish tank? A functional 20-gallon freshwater community setup with quality equipment costs approximately: - Tank: $30 to $50 - Filter (Aquaclear 30): $30 to $40 - Heater (Aqueon Pro 100W): $25 to $35 - Light (Nicrew LED): $20 to $30 - Substrate: $15 to $25 - Test kit: $25 to $30 - Water conditioner: $8 to $10 - Gravel vacuum: $12 to $15

Total: roughly $165 to $235, not including fish.