Aquarium Fish and Stuff

Setting up a successful aquarium comes down to having the right fish for your water type and experience level, paired with the right equipment to keep them healthy. "Aquarium fish and stuff" is basically the whole hobby in two words, and the answer to what you actually need depends on whether you're starting fresh, upgrading an existing tank, or figuring out why something's going wrong.

This guide covers the core categories: the essential gear every tank needs, how to choose fish that work for your setup, water chemistry basics, and the extras that make a real difference in long-term success. I'll keep it practical with specific product names and fish recommendations rather than vague advice about "providing optimal conditions."

Essential Equipment Every Aquarium Needs

Before you add a single fish, the tank itself needs to support life. Five things are non-negotiable.

Filtration

A filter is the most important piece of equipment in any aquarium. It handles biological filtration (converting toxic ammonia from fish waste into less harmful nitrate through beneficial bacteria), mechanical filtration (removing particulate waste), and sometimes chemical filtration (activated carbon removing dissolved organics and odors).

For tanks up to 20 gallons, a basic hang-on-back filter like the AquaClear 20 or the Marineland Penguin 100 is adequate. These cost $20 to $35 and run reliably for years. For 20 to 55 gallon tanks, step up to the AquaClear 50 or the Fluval 107 canister filter for better flow rates and more media capacity. Canister filters are quieter and more powerful but cost more, typically $60 to $120.

The key number to know: your filter should turn over the tank's total water volume at least 4 times per hour. A 30-gallon tank needs a filter rated for at least 120 gallons per hour.

Heater

Most tropical fish need water between 74 and 82 degrees Fahrenheit. Room temperature in most homes runs 65 to 72 degrees, which is too cold for tropical species. A submersible heater solves this.

For small tanks under 10 gallons, the Aqueon Preset 10W or the Marineland Visi-Therm 50W handle the load. For 20 to 55 gallon tanks, the Eheim Jager 150W (model 3616) or the Fluval E200 give you reliable temperature control with better accuracy than cheaper options.

Lighting

Fish need a light/dark cycle even if they don't need intense light for plant growth. Basic LED fixtures that run 8 to 10 hours per day work for fish-only tanks. The Nicrew Classic LED Aquarium Light covers tanks up to 48 inches at a low cost (around $20 to $30) and is a go-to recommendation for beginner setups.

If you want live plants, you need a light rated for plant growth, typically measured in PAR (photosynthetically active radiation). The Fluval Plant Spectrum 3.0 or the VIPARSPECTRA P1000 provide enough light for medium to high-demand plants.

Substrate

Gravel and sand both work for most freshwater fish. Natural-colored gravel (Carib Sea Super Naturals or Seachem Flourite for planted tanks) is more neutral in appearance and easier to clean than brightly colored options. Aim for about 1 pound of substrate per gallon for a standard layer depth.

For saltwater tanks, aragonite sand (CaribSea Arag-Alive) provides buffering for water chemistry and supports natural substrate biodiversity.

Test Kit

A liquid test kit is more accurate than test strips and lasts longer. The API Freshwater Master Test Kit covers ammonia, nitrite, nitrate, and pH, which are the four parameters you need to monitor during cycling and weekly maintenance. It runs about $25 and contains enough reagent for hundreds of tests.

Choosing Fish That Actually Work Together

The biggest mistake beginners make is choosing fish based on looks at the pet store without checking compatibility. Fish that look peaceful in a small store tank may be aggressive, territorial, or predatory toward each other at home.

Freshwater Fish for Beginners

Guppies (Poecilia reticulata): Hardy, colorful, and tolerant of a wide range of water parameters. They reproduce readily, which can be a feature or a problem depending on your perspective. Keep 1 male per 2 females to reduce harassment.

Corydoras catfish: Peaceful bottom dwellers that stay small (1.5 to 2.5 inches) and actively clean up leftover food from the substrate. Keep in groups of 6 or more. Corydoras paleatus (peppered corydoras) is one of the most adaptable species.

Zebra danios (Danio rerio): Fast, active schooling fish that tolerate cooler temperatures than most tropicals (65 to 77 degrees Fahrenheit). Good for unheated tanks in temperate rooms. School of 6 minimum.

Tetras: Most tetras are peaceful schooling fish for planted tanks. Neon tetras (Paracheirodon innesi) are popular but sensitive to poor water quality. Black skirt tetras and cardinal tetras are hardier alternatives.

Platies and mollies: Similar to guppies in care requirements. Mollies need slightly higher pH (7.5 to 8.0) and tolerate salt in the water better than most freshwater species.

Fish to Avoid as a Beginner

Oscars (Astronotus ocellatus): Grow to 12 to 14 inches and need 75+ gallon tanks as adults. Frequently sold as juveniles at 2 inches in stores that don't mention the adult size.

Common plecos (Hypostomus plecostomus): Sold as algae eaters but grow to 18 to 24 inches and produce enormous amounts of waste. Bristlenose plecos (Ancistrus sp.) are a better algae-eating alternative that stays under 5 inches.

Bala sharks: Schooling fish that need groups of 5 or more, grow to 12 inches, and need 120+ gallon tanks. Almost always sold far too young in stores.

Water Chemistry Basics

You don't need to become a chemist to keep fish, but understanding four basic parameters prevents most problems.

pH: Measures acid/alkalinity on a scale of 1 to 14. Most tropical freshwater fish thrive at 6.8 to 7.6. African cichlids prefer 7.8 to 8.5. Discus and most soft-water tetras prefer 6.0 to 7.0.

Ammonia: Should always be zero in an established tank. Any ammonia reading means your biological filter isn't keeping up with the waste load, either because the tank isn't cycled, the filter is new or damaged, or you're overstocked.

Nitrite: Also should be zero in an established tank. Nitrite is produced when bacteria convert ammonia, then consumed by a second type of bacteria. During the cycling process, nitrite spikes before coming down to zero.

Nitrate: Accumulates over time and is removed through water changes. Keep below 20 ppm for sensitive species, below 40 ppm for hardy fish. Regular weekly 25 percent water changes keep nitrate in check on moderately stocked tanks.

For finding supplies and equipment, our guide to the best online fish supply store covers where to get reliable equipment, live fish, and consumables shipped directly to your door.

The Extras That Actually Matter

Some "extras" make a real difference in day-to-day fishkeeping.

Air pump and airstone: An air pump like the Tetra Whisper 10 or the Hygger Aquarium Air Pump adds surface agitation that helps with oxygen exchange. Critical during hot summer months when warm water holds less dissolved oxygen.

Water conditioner: Tap water contains chlorine and chloramine that kill fish. Seachem Prime is the most concentrated and cost-effective option. A single capful treats 50 gallons. It also detoxifies ammonia and nitrite temporarily, which is useful during cycling or water quality emergencies.

Thermometer: Don't rely on the heater's built-in display. A separate digital thermometer like the Coralife Digital Thermometer or a basic glass thermometer confirms actual water temperature.

Net: A 4 to 6 inch aquarium net for catching fish during tank maintenance or transport. Have two nets for netting fish, so you can guide fish with one and catch with the other.

For a complete look at equipment needs by tank size and species, our oxygen machine for fish tank price guide covers aeration options across different budgets.

FAQ

How many fish can I put in my aquarium? The old rule of "1 inch of fish per gallon" is a rough starting point but misleading for larger or messier fish. A better approach: stock to 50 to 75 percent of your filter's capacity and watch your parameters for a month. If ammonia and nitrite stay at zero and nitrate rises slowly (under 20 ppm per week), you have room to add more. If nitrate climbs rapidly, you're at or near capacity.

Do I need live plants or can I use fake ones? Fake plants work fine for fish. They provide cover and territory markers without the care requirements of live plants. Live plants do add benefits: they consume nitrate and phosphate, produce oxygen, and outcompete algae for nutrients. But they require appropriate lighting and sometimes fertilizers, which adds complexity. Start with fake plants and add live ones when you're comfortable with the basics.

Why do my fish keep dying even though the water looks clean? Clear water is not the same as healthy water. Most of the things that kill fish, ammonia, nitrite, high nitrate, wrong pH, are invisible. The only way to know what's in your water is to test it. New tank syndrome (cycling your tank without fish or with a fish-in cycle) is the most common cause of early fish deaths. Always cycle before adding fish, or use Seachem Stability and do daily water changes if you must add fish during cycling.

What's the minimum tank size worth buying? I'd say 10 gallons for freshwater and 20 gallons for saltwater. Smaller tanks are harder to keep stable because water parameters change rapidly in low volumes. A 5-gallon tank can work for a single betta fish with careful management, but the margin for error is very thin. Larger tanks are actually easier to maintain than smaller ones because temperature and chemistry stay more stable.