Setting up a fish tank requires more than just a glass box and water. At minimum you need a tank, a filter, a heater (for tropical fish), a thermometer, a light, a water conditioner, substrate, and a test kit. That list covers the basics that keep fish alive. Beyond that, there are several optional items that make maintenance easier and the tank look better. Here's exactly what to buy and why each piece matters.
The good news is that you don't need to spend a fortune. A beginner freshwater setup for a 20-gallon tank can be assembled for $100-150 if you shop smart. This guide breaks everything down by category so you know what's essential, what's helpful, and what you can skip until later.
The Tank Itself
The tank is the obvious starting point, but size matters more than beginners expect. Bigger tanks are actually easier to manage because water chemistry stays more stable when there's more volume. A 10-gallon tank looks manageable but swings wildly in ammonia and pH; a 20-gallon gives much more room for error.
Glass vs. Acrylic
Glass tanks are heavier but more scratch-resistant and less prone to yellowing over time. Standard glass tanks from brands like Aqueon and Marineland are available at most pet stores. The Aqueon 20-Gallon Starter Kit bundles a tank, filter, heater, and light together, which is a solid value for beginners.
Acrylic tanks weigh less and offer better clarity when new, but they scratch easily during cleaning. Most hobbyists stick with glass unless weight is a specific concern.
Tank kits that bundle multiple items together can save money at the start, though the included equipment is often mid-range. As you gain experience, you'll likely upgrade components anyway.
Filtration
A filter is non-negotiable. Fish produce ammonia through waste and respiration, and ammonia is toxic. Your filter converts ammonia to nitrite, then to less harmful nitrate, through a process called the nitrogen cycle. No filter, no surviving fish.
Types of Filters
HOB (hang-on-back) filters are the most common choice for beginners. The AquaClear 30 and Fluval C4 are well-regarded options that handle tanks up to 40 gallons. HOB filters are easy to maintain and provide good mechanical and biological filtration.
Canister filters sit below the tank and process larger water volumes more efficiently. The Fluval 207 handles tanks up to 45 gallons; the Fluval 407 goes up to 100 gallons. Canister filters are quieter and more powerful than HOB units but cost more and require more effort to clean.
Sponge filters work well for small tanks and breeding setups. They're cheap, gentle, and excellent for biological filtration, but they don't do much for mechanical filtration (removing particles).
Size your filter for at least 4-5 times your tank volume in turnover per hour. A 30-gallon tank should have a filter rated for 120-150 gallons per hour minimum.
Heating and Temperature Control
Most tropical fish need water between 74-80°F. Goldfish and some other cold-water species can tolerate room temperature, but if you're keeping bettas, tetras, cichlids, or most common community fish, you need a heater.
The Eheim Jager is a trusted name in aquarium heaters and comes in sizes from 25W to 300W. For a 20-gallon tank, a 100W unit provides enough buffer for temperature fluctuations in most homes. The Aqueon Pro heater is another reliable option that includes an indicator light showing whether the unit is actively heating.
Always pair your heater with a separate thermometer. The Zacro LCD digital thermometer ($8-10) gives accurate readings without relying on the heater's built-in thermostat, which can drift over time.
For tanks over 55 gallons or sensitive fish that need precise temperatures, an external temperature controller like the Inkbird ITC-306A plugs between the heater and the outlet and cuts power if the temperature exceeds a set maximum.
Lighting
Light isn't optional for planted tanks, but even fish-only tanks benefit from a light to show off the fish and support any live plants you might add later. Most tank kits include a basic light, which is fine for low-light plants or fish-only setups.
For planted tanks, the Fluval Plant 3.0 and the Current USA Planted+ 24/7 are two popular LED options that provide the full light spectrum plants need. For fish-only tanks, any LED strip light that fits the tank hood works fine.
Lighting duration matters too. Most aquarium lights should run 8-10 hours per day. A cheap outlet timer (about $10) automates this and reduces algae growth by keeping the photoperiod consistent.
Substrate
What you put on the bottom of the tank affects both aesthetics and water chemistry. Gravel is the classic choice, easy to clean with a gravel vacuum, and available in endless colors. Plain natural-colored gravel or black aquarium substrate looks more natural and makes fish colors pop.
For planted tanks, you need a nutrient-rich substrate. Fluval Stratum and Seachem Flourite are two popular options that support root growth without dramatically altering pH. Plain gravel doesn't provide nutrients for plants, so you'd need to supplement with root tabs.
Aim for 1-2 inches of substrate depth for fish-only tanks, and 2-3 inches for planted tanks so roots have room to anchor.
Water Conditioner and Cycling Supplies
Tap water contains chlorine and chloramines that kill fish instantly. Seachem Prime is the gold standard water conditioner. It neutralizes chlorine, chloramines, and temporarily detoxifies ammonia and nitrite, which makes it especially useful during the cycling process. A single 100ml bottle treats up to 1,000 gallons.
Speaking of cycling: don't add fish to an uncycled tank. The nitrogen cycle takes 4-6 weeks to establish naturally. You can speed it up by seeding the filter with beneficial bacteria from an established tank or using products like Tetra SafeStart Plus, which adds live bacteria directly. Our guide to using an oxygen machine for fish tank covers how aeration supports the cycling process.
For buying a broader starter pack of supplies online, our Best Online Fish Supply Store guide lists the most reliable retailers for getting everything shipped together.
Test Kits and Water Quality Monitoring
The API Master Test Kit is the most complete liquid test kit for freshwater tanks. It tests ammonia, nitrite, nitrate, and pH, which are the four parameters you'll monitor constantly during cycling and throughout the life of the tank. Liquid test kits are more accurate than test strips and only slightly more work.
Once your tank is cycled, you'll test weekly during the first few months, then monthly once things stabilize. Buy the master kit, not individual tests. The price difference is small but the convenience is significant.
A second useful tool is a GH/KH test kit if you plan to keep fish with specific hardness requirements, like African cichlids (hard water) or discus (soft water).
Decorations and Equipment Add-Ons
Fish need hiding spots to feel secure and reduce stress. A bare tank with nowhere to hide produces anxious fish that hide in corners instead. Rocks, driftwood, caves, and artificial plants all work. Natural driftwood can soften water pH over time, which suits soft-water species. Ceramic caves and terra cotta pots provide hiding places without affecting chemistry.
An air pump and air stone aren't strictly required if you have a filter providing surface agitation, but they help in warmer water (warm water holds less oxygen) and during power outages when the filter isn't running. The Tetra Whisper AP series is a reliable budget air pump. Connect it to a check valve to prevent back-siphoning if power cuts out.
A gravel vacuum makes water changes dramatically easier. The Python No Spill Clean and Fill system hooks directly to your faucet for no-bucket water changes, which is worth the $30-40 price if you have a tank larger than 20 gallons.
FAQ
How much does it cost to set up a basic fish tank?
A 20-gallon freshwater starter setup costs $100-200 for everything including the tank, filter, heater, light, substrate, water conditioner, and test kit. Buying a kit bundle saves money versus purchasing components individually. Ongoing costs include food ($5-10/month), electricity, and replacement filter media.
Do I need a heater for a goldfish tank?
Goldfish are cold-water fish and don't need a heater as long as your home stays above 65°F. Below that, metabolism slows and immune function drops. If your home gets cold in winter, a low-wattage heater set to 65-68°F gives them a buffer without overheating.
How long do I have to wait before adding fish?
You should wait until the tank completes the nitrogen cycle, which takes 4-6 weeks naturally. You can speed this up by adding beneficial bacteria products like Tetra SafeStart Plus or Dr. Tim's One and Only, and by keeping the ammonia source consistent throughout cycling. Don't add fish until ammonia and nitrite both read 0 ppm.
How often do I need to do water changes?
For a stocked freshwater tank, a 25-30% water change weekly is the standard recommendation. Overstocked tanks or heavily fed tanks may need more frequent changes. Always treat new tap water with dechlorinator before adding it to the tank.
Key Takeaways
Start with the basics: tank, filter, heater, thermometer, light, substrate, water conditioner, and a test kit. Cycle the tank before adding fish. A 20-gallon tank is a better starting point than a 10-gallon because it's more stable and forgiving of beginner mistakes. Get a gravel vacuum before your first water change and you'll wonder how anyone manages without one.