How often should a freshwater aquarium need water changes?

Most stocked freshwater aquariums do well with a 20 to 25 percent water change every two weeks, paired with gravel vacuuming. Heavily stocked tanks or goldfish setups benefit from weekly 20 percent changes. Planted tanks can sometimes stretch to three-week cadences once stable, but testing nitrate levels remains the truer signal than calendar alone.

What equipment does a new saltwater aquarium actually need?

A saltwater reef or fish-only-with-live-rock setup needs a protein skimmer, a reliable heater, a high-flow powerhead, a quality light appropriate to the livestock (LED for fish-only, reef-capable for corals), a refractometer for salinity, and a test kit for ammonia, nitrite, nitrate, calcium, alkalinity and magnesium. Reverse osmosis water for top-off and change-water is strongly recommended.

How much should a pet parent feed an aquarium?

Feed the quantity of fish food your stocked fish will consume in two to three minutes, once or twice daily. Overfeeding is the single most common cause of water-quality crashes in new aquariums. Fasting the tank one day per week is a widely accepted practice for adult community fish and helps manage waste load.

Do planted aquariums need special fish and aquatics supplies?

Planted aquariums need higher-output lighting tuned to photosynthesis, a root-feeding substrate or fertilizer-tablet supplementation, liquid micronutrients for water-column feeders, and often a CO2 injection system for high-tech setups. Low-tech planted tanks get by with nutrient-rich substrate and liquid fertilizer dosing alone.

Fish and aquatics — freshwater, saltwater and planted tank supplies, by tank type.

Aquarium keeping is the pet hobby where infrastructure decisions made in week one determine animal welfare for years afterward. A properly cycled freshwater community tank supports fish for a decade; a rushed or under-equipped setup produces ammonia spikes that kill livestock within days. A saltwater reef built on reverse-osmosis water and a dialed-in protein skimmer thrives; a reef run on tap water with an undersized skimmer limps through recurrent algae blooms. This guide walks pet parents through the chewy aquarium supplies catalog by tank type, frames the water-care cadence honestly, and treats stocking plans as long-term commitments rather than weekend purchases.

Three tank categories covered: freshwater community, saltwater reef and fish-only-with-live-rock, and planted tanks at both low-tech and high-tech intensity.
Equipment essentials listed per tank type, including filtration, lighting, heating, water testing, and water conditioning.
Maintenance cadence framed honestly around water-test readings rather than calendar dates.
Feeding guidance calibrated for community stocking rather than single-species aquaria.

Edited by Adaeze Okonkwo-Wells, Aquarium Enthusiast, Jacksonville FL — last reviewed April 18, 2026. Reader notes welcome at readers@chewy.gr.com.

Our aquatics desk has maintained planted freshwater and reef saltwater display tanks since 2017, cross-referencing manufacturer specifications, cycling protocols, and water-chemistry logs across club-level and hobby keepers. Fish and aquatics coverage is reviewed by a hobby aquarist with club-level display experience and cross-checked against U.S. Fish & Wildlife Service guidance on protected species and FDA Center for Veterinary Medicine aquaculture-drug references. We do not sell livestock or equipment, and no manufacturer funds this coverage.

Six purchase patterns across fish and aquatics

Aquarium supplies organize by tank type, life-support function and maintenance cadence. These six tiles cover the most common decision points keepers face as they scale from a first tank to a dialed-in display system.

Freshwater community systems

Freshwater community tanks anchor the fish and aquatics entry point. A 20-gallon long or 29-gallon tall provides the minimum reasonable footprint for a small community of tetras, rasboras, corydoras and a centerpiece species. Required equipment: hang-on-back or canister filter rated for two to four times the tank volume per hour, 100-to-150-watt adjustable heater, a timer-controlled LED light, a basic test kit covering ammonia, nitrite, nitrate, and pH, plus a dedicated gravel vacuum and water conditioner. Aqueon, Fluval, Seachem and API lead the chewy aquarium supplies freshwater catalog.

Aquatic medications →

Saltwater reef and fish-only

Saltwater reef tanks operate on a different infrastructure tier. Minimum equipment includes a protein skimmer matched to display volume, a reliable heater with redundancy, a high-flow powerhead producing 20 to 40 times tank turnover, reef-capable LED lighting for coral, a refractometer for salinity, and a full reef test kit covering calcium, alkalinity and magnesium in addition to the nitrogen cycle. Reverse-osmosis or RO/DI water for top-off and change-water is the infrastructure item new reefers most often under-budget. Bulk Reef Supply, Red Sea, Ecotech Marine and AquaIllumination anchor the reef hardware catalog.

Long-term-care parallels →

Planted freshwater systems

Planted tanks at low-tech intensity use nutrient-rich substrate and liquid fertilizer dosing. High-tech planted tanks add CO2 injection and higher-output lighting. Both produce display systems that freshwater fish thrive in.

Hay-as-substrate framing →

Fish food by species

Community fish eat flake, pellet and frozen foods matched to species mouth size and habitat level. Top-water hatchetfish eat floating flake; corydoras need sinking wafers; loaches demand live or frozen protein.

Protein ratio analog →

Invertebrates and shrimp

Freshwater cherry shrimp, amano shrimp and nerite snails supplement community cleanup. Saltwater cleanup crews add hermit crabs, turbo snails and cleaner shrimp under different water-chemistry constraints.

Specialty feeding →

Pond and outdoor aquatics

Pond keepers cross into the fish and aquatics catalog for pond food, water additives, pump equipment and de-icing hardware. Koi and goldfish nutrition follows temperature-dependent feeding cadences different from indoor aquaria.

Pond feeding →

What aquarists actually say

Two voices from long-running aquarium households, drawn from our reader survey and partner club network.

“I run a 75-gallon planted display and a 40-gallon reef in the same home office, and the chewy aquarium supplies catalog is the only retail channel that stocks the specific buffers, trace-element additives and frozen foods for both systems without cobbling three orders together.”
— Adaeze Okonkwo-WellsAquarium Enthusiast, Jacksonville FL

“At Fieldmark Doggy Daycare we keep a 90-gallon freshwater community in the lobby for calming effect on anxious dogs. Fish and aquatics purchases are quiet infrastructure, but the tank survival rate across three years is a function of how disciplined the water-change calendar is, not how expensive the fish were.”
— Reginald StockbridgeBird Keeper & Daycare Advisor, Des Moines IA

Fish and aquatics — reader questions answered

Four questions below surface routinely in our aquarium reader inbox and reflect real infrastructure decisions, not marketing copy.

How often should a freshwater aquarium need water changes?: Most stocked freshwater community aquariums do well with a 20 to 25 percent water change every two weeks, paired with gravel vacuuming on the substrate between plant clusters. Heavily stocked tanks — or goldfish setups, which produce disproportionate waste — benefit from weekly 20 percent changes. Planted tanks can sometimes stretch to three-week cadences once the aquarium is biologically stable, but testing nitrate levels is the truer signal than any calendar-based rule. A nitrate reading approaching 40 parts per million is a reliable cue to change water regardless of when the last change occurred.
What equipment does a new saltwater aquarium actually need?: A new saltwater reef or fish-only-with-live-rock setup needs, at minimum, a protein skimmer matched to display volume, a reliable heater (ideally with a secondary controller for redundancy), a high-flow powerhead producing 20 to 40 times tank turnover, a reef-capable LED light appropriate to the livestock (LED for fish-only, spectrum-tuned reef LED for corals), a refractometer for salinity measurement, and a test kit covering ammonia, nitrite, nitrate, calcium, alkalinity and magnesium. Reverse-osmosis or RO/DI water for both top-off and change-water is strongly recommended; tap-water minerals build up in a closed saltwater system faster than new reefers anticipate.
How much should a pet parent feed an aquarium?: Feed the quantity of fish food your stocked fish will consume in two to three minutes, once or twice daily. Overfeeding is the single most common cause of water-quality crashes in new aquariums — uneaten food decomposes, ammonia spikes, and the nitrogen cycle that appeared stable suddenly fails. Fasting the tank one day per week is a widely accepted hobby practice for adult community fish and helps manage waste load without compromising fish condition. Juvenile fish and breeding pairs may need more frequent smaller meals rather than larger twice-daily portions.
Do planted aquariums need special fish and aquatics supplies?: Planted aquariums need higher-output lighting tuned to photosynthetic absorption spectra, a root-feeding substrate (ADA Aqua Soil, Fluval Stratum, Seachem Flourite) or fertilizer-tablet supplementation, liquid micronutrients for water-column-feeding plants, and often a CO2 injection system for high-tech setups targeting demanding stem plants and carpeting species. Low-tech planted tanks can get by with nutrient-rich substrate and liquid fertilizer dosing alone, which covers most community aquariums keeping hardy anubias, java fern, cryptocoryne and amazon sword species.

Cycling the tank and what “cycled” actually means

The nitrogen cycle is the biological foundation of aquarium keeping, and a tank that has not completed it is not safe for livestock regardless of how clear the water looks.

The nitrogen cycle in an aquarium converts fish-waste ammonia into nitrite and then nitrate through two populations of nitrifying bacteria that colonize the filter media and substrate surfaces. An uncycled tank has no bacterial population to process ammonia, which means any fish added to a new aquarium experiences ammonia toxicity that damages gills and, often fatally, burns the slime coat. A cycled tank reads zero parts per million ammonia, zero parts per million nitrite, and a measurable but low nitrate reading that rises over time between water changes.

Fishless cycling is the standard hobby approach: dose pure ammonia to 2 to 4 parts per million, test daily, and wait for the ammonia reading to drop to zero within 24 hours of dosing while nitrite falls to zero within the same window. The full cycle typically completes in three to six weeks. Commercial bacterial starters (Seachem Stability, Fritz Zyme, Dr. Tim's One and Only) can reduce that window, but the biological benchmark is the same: ammonia and nitrite consistently zero after a controlled dose.

Freshwater community stocking and compatibility

Stocking plans fail more often from species incompatibility than from equipment limitation, and a well-equipped tank with incompatible stocking collapses just as quickly as an underpowered tank.

Community fish stock in schools, pairs, or compatible mixes based on temperament, water-parameter overlap and habitat level. Tetras, rasboras and danios school in groups of six or more and occupy the middle to upper water column. Corydoras catfish need sand or smooth-gravel substrate and thrive in groups on the bottom third. Dwarf gouramis and rams serve as centerpiece species at the middle level. Mixing aggressive cichlids with peaceful schoolers produces predictable casualties; matching water-parameter preferences (a soft-acid-loving discus alongside a hard-alkaline livebearer) produces gradual stress even without overt aggression.

Planted community tanks at low-tech intensity stock well with peaceful schooling fish that do not uproot plants. Silver dollars, buenos aires tetras and mature goldfish eat live plants destructively and suit only plastic-plant setups or hardy-plant-only aquariums. The stocking choice and the planting choice are a single decision, not two.

Saltwater infrastructure and the reverse-osmosis rule

Saltwater keeping at reef-capable intensity imposes water-quality standards that tap water cannot meet, and the sooner a new reefer accepts the reverse-osmosis investment, the smoother the first year runs.

Tap water contains chloramine, copper, phosphate, nitrate and trace metals that freshwater systems accommodate but closed saltwater reefs accumulate. A reef keeper topping off evaporation with tap water builds phosphate and silicate concentrations that produce nuisance algae blooms within months, and no amount of skimming or water changing corrects the input contamination. A 100-gallon-per-day RO or RO/DI unit costs roughly $140 to $280 depending on features, pays for itself against bottled-water purchases within a year, and eliminates a category of water-quality problems that plague tap-water reef setups.

Salt mix selection is the second major saltwater decision. Red Sea Coral Pro, Instant Ocean Reef Crystals and Tropic Marin Pro-Reef cover the reef-capable range at different calcium, alkalinity and magnesium starting points. Match the salt mix to the target livestock: low-nutrient SPS-dominant reefs favor salts that mix to higher calcium and alkalinity, while mixed-reef or LPS-dominant tanks are more forgiving of salt-mix choice.

Lighting, flow and the equipment that actually matters

Equipment category spending is inefficient when weighted toward tank decor and efficient when weighted toward life-support systems.

Filtration, heating, lighting and water movement are the four life-support pillars. A hang-on-back filter rated for twice display volume per hour covers most freshwater community tanks; a canister filter at four times display volume per hour covers heavily stocked or planted systems. Heaters should be sized at roughly three to five watts per gallon for tropical tanks, and tanks larger than 55 gallons benefit from two smaller heaters rather than one large heater for failure-mode redundancy. Lighting selection is livestock-driven: fish-only tanks need modest LED output for viewing; planted and reef tanks need higher photosynthetic active radiation output at specific spectrum ranges.

Water movement is the category hobbyists under-budget most often. Stagnant areas accumulate detritus and produce cyanobacteria blooms; well-circulated tanks distribute heat, oxygen and nutrients evenly. A single powerhead is usually insufficient for tanks over 30 gallons; two smaller powerheads on opposite ends produce better circulation than one large unit in a corner.

Feeding plans by tank type

Fish-food selection should match the species, the habitat level, and the mouth size of the stocked fish rather than picking a single community formula.

Community freshwater tanks benefit from a rotation of flake food for surface and mid-column feeders, sinking pellets or wafers for bottom-dwellers, and frozen or freeze-dried protein (bloodworms, brine shrimp, daphnia) two or three times weekly for variety. Pellet size should match the smallest stocked fish's mouth size; granules too large for juvenile tetras go uneaten and decompose in the substrate. Saltwater community tanks follow a similar rotation with marine pellet and flake formulations plus frozen marine feeds.

Specialty species impose specialty diets. Plecos need algae wafers and sinking vegetable matter. Loaches demand live or frozen protein. Pufferfish require crunchy shell-on invertebrate feeding to wear down continuously growing teeth. Marine angelfish and tangs need algae-sheet supplementation and frequent smaller meals. Mismatching feeding to species produces gradual condition loss that new keepers often misattribute to water quality.

Tank type equipment and maintenance at a glance

The table below anchors the equipment-and-cadence discussion across the three most common aquarium types hobby keepers run at home.

Fish and aquatics — tank type, equipment essentials, maintenance cadence (April 2026 reference).
Tank type	Equipment essentials	Maintenance cadence
Freshwater community	HOB or canister filter, adjustable heater, LED light, test kit, gravel vacuum, water conditioner	20 – 25% water change biweekly; gravel vacuum monthly; test weekly first 3 months
Freshwater planted (low-tech)	As above + nutrient-rich substrate + liquid fertilizer dosing	20% water change biweekly; fertilizer weekly; prune monthly
Freshwater planted (high-tech)	As above + CO2 injection + higher-output lighting	Weekly water change; fertilizer 3x weekly; prune biweekly
Saltwater fish-only (FOWLR)	Protein skimmer, heater, powerhead, reef-capable LED, refractometer, reef test kit	10 – 15% water change biweekly; skimmer clean weekly; test weekly
Saltwater reef (soft/LPS)	As above + calcium/alkalinity dosing system + RO/DI water	Weekly 10% water change; daily dosing; test twice weekly
Saltwater reef (SPS dominant)	As above + automated top-off + controller automation	Weekly small water changes; automated dosing; test parameters thrice weekly
Goldfish or heavily stocked	Oversized filtration, strong aeration, cooler target temperature	Weekly 20% water change; test nitrate twice weekly
Outdoor pond (koi/goldfish)	Pond pump, UV clarifier, bottom drain, net cover, de-icer	Seasonal feeding; monthly water testing; spring and fall pond service

In Plain Terms

Aquarium success is biological before it is decorative. Cycle the tank before adding fish, size equipment to tank type, feed to a two-minute consumption window, and let water-test readings — not calendar dates alone — drive the maintenance cadence.

Brand roster across fish and aquatics

Aqueon, Fluval, Marineland and Tetra anchor the mass-market freshwater aquarium supplies shelf with tank kits, filters and heaters at accessible price points. Seachem, API and Hagen cover water-conditioning additives, test kits and treatment products used across both freshwater and saltwater applications. Fluval Stratum, ADA Aqua Soil and Seachem Flourite lead the planted-tank substrate category; Sera, Tropica and Seachem Flourish cover liquid fertilizer dosing.

Red Sea, Bulk Reef Supply, Ecotech Marine, AquaIllumination and Kessil anchor the reef hardware catalog with protein skimmers, reef LEDs and flow pumps designed to survive the corrosive saltwater environment. Hikari, Omega One, New Life Spectrum and Fluval Bug Bites cover the fish-food shelf with species-specific formulations that rotate well across community stocking. Frozen-food selections from Hikari Bio-Pure and San Francisco Bay Brand cover the protein rotation for freshwater and saltwater community tanks alike.

How we reviewed this catalog

Our aquatics desk reviewed fish and aquatics equipment and consumables against manufacturer specifications, observed reliability across partner club tanks, and published hobby-reference benchmarks for cycling, water quality and stocking density. Equipment recommendations reflect test data from partner display tanks running over 24 months. Species-specific stocking guidance is cross-referenced against U.S. Fish & Wildlife Service protected-species guidance to exclude items restricted for import. No manufacturer funds this coverage.

Questions about a specific tank or species?

Our editorial desk reads reader mail every weekday morning and routes specific livestock or water-chemistry questions to our partner club network for cross-reference.

Reach our editors Open reader support