To set up a fish tank, you need at minimum a tank, a filter, a heater (for tropical fish), lighting, a lid, substrate, a thermometer, a water conditioner, and a test kit. That's the foundation that keeps fish alive and healthy. Everything beyond that, decorations, air pumps, automatic feeders, is either improvement or convenience. Getting the essentials right from the start saves you from the most common beginner mistakes.
This guide covers each equipment piece, what it does, what to look for when buying, and where things go wrong. By the end, you'll have a clear shopping list based on the actual tank you're setting up.
Tank and Stand
The tank is the obvious starting point, but size matters more than most people realize. Smaller tanks are harder to manage, not easier. A 10-gallon tank has a water volume where a dead snail can spike ammonia within a day. A 29-gallon tank is much more forgiving of minor fluctuations.
For a first tank, 20 gallons long is a practical sweet spot: it accommodates a good variety of community fish, fits on a standard aquarium stand, and doesn't require huge amounts of water treatment for changes. The Aqueon 20-gallon long glass tank is a common starting point at around $40 to $60.
Tank Stand
Aquariums are heavy. A gallon of water weighs 8.3 pounds. A 29-gallon tank with substrate, rock, and equipment weighs 300+ pounds. Most household furniture is not rated for this. Use a proper aquarium stand rated for the tank size. Iron stands from Aqueon or wooden stands from Imagitarium handle the weight and position the tank at a comfortable viewing height.
Filter
The filter handles biological filtration (breaking down fish waste into less harmful compounds), mechanical filtration (trapping particles), and optional chemical filtration (activated carbon removing odors and colors). It's the most important piece of functional equipment in the tank.
Hang-on-Back Filters
HOB filters are the starting point for most freshwater setups. The Aquaclear 50 is consistently rated as the best budget HOB filter for tanks up to 60 gallons. It runs about $35 and has more media capacity than most competitors. The Seachem Tidal 55 is another strong option with a surface skimmer and adjustable flow for around $45.
Filter flow rate should be 5 to 10 times your tank volume per hour. A 20-gallon tank needs a filter rated 100 to 200 GPH. The AquaClear 50 flows 200 GPH, making it appropriate even for 30-gallon tanks.
Canister Filters
For tanks over 55 gallons or densely stocked setups, canister filters are more powerful and versatile. The Fluval 307 handles up to 70 gallons and costs about $120. Canisters hold more biological media and produce less surface disturbance than HOBs, which matters in CO2-injected planted tanks.
Heater
Most fish sold in aquarium stores are tropical species requiring 74 to 82 degrees Fahrenheit. Without a heater, room temperature water (typically 65 to 70 degrees) will stress tropical fish and make them susceptible to ich and other diseases.
Heater Sizing
Use 3 to 5 watts per gallon as a guideline. A 20-gallon tank needs a 50 to 100-watt heater. The Eheim Jager 75W is a reliable choice for tanks up to 20 gallons, accurate to within 0.5 degrees, and costs about $25. The Cobalt Aquatics Neo-Therm is a premium option with an electronic controller and flat profile.
For tanks over 40 gallons, use two smaller heaters rather than one large one. If one heater fails stuck-off, the second keeps the tank from crashing. Position heaters near a powerhead or filter intake so warm water circulates evenly.
Separate Temperature Controller
An external temperature controller like the Inkbird ITC-306 ($25) plugs between the heater and outlet and cuts power if temperature exceeds your set maximum. This protects against heater malfunction that could cook your fish. Not essential, but strongly recommended for expensive or irreplaceable fish.
Lighting
Lighting is functional for plants and aesthetic for viewing fish.
Low-Light or Fish-Only Tanks
A basic LED strip that covers the tank length is sufficient. The Aqueon LED Fish Tank Hood combines a glass lid and LED strip in one unit. For viewing fish without growing plants, any warm-white or full-spectrum LED works.
Planted Tanks
Plants need specific light intensity and duration. The Fluval Plant 3.0 LED adjusts intensity and spectrum through an app and supports everything from low-light Java Ferns to medium-light stem plants. For high-light demanding plants, the Finnex Planted+ 24/7 CRV provides more par output and includes a 24-hour automated light cycle.
Run lights on a timer (7 to 10 hours daily for planted tanks) to prevent algae from taking advantage of irregular lighting.
Substrate
Gravel and sand serve as the tank bottom and, in planted tanks, as a growth medium for plant roots.
Gravel
Standard aquarium gravel like Carib Sea Super Naturals or Aqueon Aquarium Gravel is inert, easy to vacuum, and compatible with all fish. Use 1 to 2 pounds per gallon for a standard depth layer.
Sand
Pool filter sand or aquarium sand from CaribSea (their Crystal River or Moonlight Sand) looks natural and is preferred by bottom-dwelling fish like corydoras and kuhli loaches. Sand is harder to vacuum without disturbing it but creates a cleaner aesthetic.
Planted Substrates
Seachem Flourite, Eco-Complete, and ADA Aqua Soil contain nutrients that support rooted plants. ADA Aqua Soil is the premium option and provides the best plant growth but requires an initial cycling period as it leaches ammonia. Eco-Complete is a solid budget option that doesn't require conditioning before use.
You can also browse the best online fish supply store to compare substrate brands and prices across multiple retailers.
Water Conditioner and Test Kit
These two items should be on the counter before any water goes in the tank.
Water Conditioner
Seachem Prime is the industry standard water conditioner. It neutralizes chlorine and chloramine in tap water and temporarily detoxifies ammonia and nitrite, which is useful during the nitrogen cycle. One 250mL bottle treats 5,000 gallons and costs about $10. Always add Prime to new water before it enters the tank.
Liquid Test Kit
The API Freshwater Master Test Kit ($25) covers ammonia, nitrite, nitrate, and pH with enough reagent for 800 total tests. Liquid tests are significantly more accurate than test strips. Test ammonia and nitrite daily during the first 4 to 6 weeks of cycling, and weekly after the tank is established.
Air Pump
An air pump is technically optional if your filter provides sufficient surface agitation, but it's useful backup aeration and comes in handy during hot weather when dissolved oxygen drops. The Tetra Whisper Air Pump is quiet and handles tanks up to 40 gallons for under $15. Pair it with a basic air stone and airline tubing.
For a more detailed look at air pumps and other equipment at different price tiers, the oxygen machine for fish tank guide covers the options specifically.
FAQ
In what order should I set up a fish tank? Set up the stand, place the tank, add substrate, add decorations, fill with conditioned water, then add filter and heater. Run the tank for 4 to 6 weeks to cycle before adding fish, testing ammonia and nitrite throughout. The cycle is complete when ammonia reads zero, nitrite reads zero, and nitrate is rising.
What is the nitrogen cycle and why does it matter? The nitrogen cycle is the process by which beneficial bacteria colonize your filter media and convert toxic ammonia (from fish waste) into nitrite (also toxic) and then into nitrate (much less harmful). Without an established cycle, ammonia builds up and kills fish. Cycling before adding fish is the single most important step beginners skip.
How many fish can I put in my tank? A rough starting guide is 1 inch of adult fish body length per gallon of water. A 20-gallon tank accommodates about 20 inches of adult fish, so ten 2-inch tetras or five 4-inch barbs. This is a guideline, not a hard rule. Fish bioload, aggression, and territorial behavior all affect how many fish a tank can support.
Do I need a lid for my fish tank? Yes, for almost all setups. Lids prevent jumping (many popular fish like danios, gouramis, and bettas jump), reduce evaporation, and keep out dust and pets. The exception is open-top tanks deliberately designed for plants that grow above the waterline, and even those benefit from some form of cover.
Key Takeaways
Every fish tank needs a filter, heater, thermometer, appropriate lighting, a lid, substrate, water conditioner, and a test kit. These are the non-negotiable items. Everything else is enhancement.
Spend the most budget on your filter and heater. These two items have the biggest impact on fish survival and the highest failure rate in cheap versions. A $35 AquaClear filter and a $25 Eheim Jager heater will outlast and outperform most kit-grade equipment and make the difference between a frustrating first tank and a successful one.