Yes, you need aquarium equipment to keep fish alive. At a bare minimum, that means a tank, a filter, a heater for tropical species, and a water conditioner for tap water. Without a filter, ammonia accumulates and kills fish within days. Without a heater, tropical fish become lethargic, stop eating, and eventually die from cold stress. Everything else, from CO2 systems to automatic feeders to fancy wave makers, is optional depending on what you're keeping and how hands-on you want to be.
That said, the line between "required" and "optional" shifts based on your fish, your tank setup, and your schedule. A betta fish in a heated 5-gallon tank needs less equipment than a reef aquarium or a heavily planted Dutch-style tank. This guide walks through every major piece of equipment, what it actually does, and whether you realistically need it for a typical setup.
What Every Fish Tank Needs
These aren't optional. Skipping any of these in a fish tank leads to dead fish, typically within a week.
A Filter
Beneficial bacteria live in your filter media and break down toxic ammonia from fish waste into nitrite, then into less harmful nitrate. This process is called the nitrogen cycle. Without a filter running 24/7, ammonia spikes every day your fish are in the tank.
For a 10-gallon beginner tank, something like the Aqueon QuietFlow 10 or an Aqueon Quietflow 20 hang-on-back filter costs under $25 and runs reliably for years. For larger tanks, a canister like the Fluval 307 handles tanks up to 70 gallons and gives you more media capacity.
Don't undersize your filter to save money. A filter rated for a 20-gallon tank on a 30-gallon stocked tank will struggle.
A Heater (For Tropical Fish)
Most popular aquarium fish come from tropical regions of South America, Africa, and Southeast Asia where water temperatures stay between 74°F and 82°F year-round. Your house, especially in winter, may drop to 65°F or cooler. That temperature gap stresses fish, suppresses their immune systems, and makes them susceptible to ich and other diseases.
The Eheim Jager 100W or Fluval E100 are reliable choices for tanks under 30 gallons. If you're keeping temperate species like goldfish, white cloud mountain minnows, or native North American fish, you can skip the heater since they prefer cooler water anyway.
A Thermometer
You can't confirm your heater is working without one. A simple digital probe thermometer like the Zacro LCD Digital Aquarium Thermometer costs around $10 and gives you an accurate reading at all times. The stick-on strip thermometers included in many starter kits are inaccurate and fade over time.
A Water Conditioner
Tap water contains chlorine or chloramine to kill bacteria. Those same chemicals kill the beneficial bacteria in your filter and directly harm fish gills. Seachem Prime is the most concentrated and versatile conditioner available. It neutralizes chlorine, chloramine, ammonia, and nitrite with a small dose, and a single 250mL bottle treats over 5,000 gallons.
Equipment That Depends on What You're Keeping
Some equipment is mandatory for certain setups but completely unnecessary for others.
CO2 Systems
CO2 injection is required only if you want high-growth planted tanks with demanding carpet plants like Hemianthus callitrichoides (HC Cuba) or stem plants under high-intensity light. For low-light tanks with hardy plants like Java fern, Anubias nana, or hornwort, CO2 is unnecessary. Those plants grow fine using the CO2 naturally produced by your fish.
A pressurized CO2 system with a regulator, solenoid, and diffuser costs $100 to $300 depending on the brand. The Aquatek Mini CO2 Regulator paired with a standard paintball or 5lb tank is a popular starting point. Budget-minded planted tank keepers use DIY yeast CO2 setups for under $20, though output is inconsistent.
UV Sterilizers
UV sterilizers kill free-floating pathogens, algae spores, and bacteria as water passes through a chamber with a UV bulb. They're most useful in tanks with repeated disease outbreaks or green water algae problems. For most community tanks, a good filter and proper stocking levels make a UV sterilizer unnecessary.
If you're running a quarantine setup or a display tank with expensive fish, the Green Killing Machine 9W or Coralife Turbo-Twist 3X are reasonable mid-range options. UV sterilizers don't replace filtration. They supplement it.
Protein Skimmers
Protein skimmers are only relevant for marine (saltwater) tanks. They remove dissolved organic compounds before they break down into ammonia. For freshwater tanks, ignore them entirely.
Equipment That Makes Life Easier But Isn't Mandatory
Automatic Feeders
An automatic feeder dispenses food on a timer when you're away. The Eheim Automatic Feeder 3581 is reliable and programmable. Fish can go a week or more without food safely, so a feeder is optional unless you travel frequently.
Aquarium Controllers
Controllers like the Neptune Apex or GHL Profilux monitor and automate temperature, lighting, flow rates, and dosing for complex reef tanks. They cost $300 to $600 and are overkill for anything except a serious reef setup. For freshwater fish tanks, you don't need one.
Refugiums and Sumps
Sumps are additional tanks connected to your main display tank, usually positioned in the cabinet below. They add water volume (which dilutes toxins and stabilizes temperature), provide space for equipment you want out of the display, and can hold a refugium for growing macroalgae that exports nutrients. Sumps are common in reef tanks and useful in large freshwater setups, but they're not required for most community tanks.
What Happens If You Skip Required Equipment
Skipping a filter in a fish tank means ammonia accumulates from fish waste every day. Ammonia above 0.5 ppm causes chemical burns to fish gills. Above 1 to 2 ppm, fish begin dying. Without water changes every single day, an unfiltered tank cannot sustain fish long-term.
Skipping a heater in a tropical tank is less immediately fatal but equally damaging over time. Temperatures below 68°F suppress fish immune function. Ich (white spot disease) outbreaks commonly follow cold stress events. A 20-gallon tropical tank without a heater in a 65°F house will have sick fish within a few weeks.
If you're shopping for a first setup and want help sorting through specific product options, our Best Aquarium Equipment guide covers the most reliable choices across all the essentials. The Top Aquarium Equipment page narrows it down by tank size and fish type.
Frequently Asked Questions
Can fish survive without a filter if I do frequent water changes?
Technically yes, but it requires daily partial water changes to keep ammonia below toxic levels. Fish breeders sometimes use this method for small containers. For a display tank, a filter is far more practical and far less work.
Do I need a light if I don't have plants?
Fish don't strictly need a light to survive, but a consistent light-dark cycle reduces stress. Without it, fish in a dark room become skittish and their colors fade. A basic LED hood light on a timer is inexpensive and worth having even for fish-only tanks.
Is an air pump required?
An air pump is not required if your filter provides sufficient surface agitation for gas exchange. Most hang-on-back and canister filters return water at the surface, which aerates the tank naturally. Air pumps become more useful in warm tanks where oxygen solubility drops, or in heavily stocked setups.
Do I need a quarantine tank?
You don't need one to get started, but experienced hobbyists consider it essential. A quarantine tank lets you observe new fish for 2 to 4 weeks before introducing them to your display tank, preventing the spread of disease. A simple 10-gallon tank with a sponge filter and heater works perfectly as a quarantine setup.