Freshwater tanks cost less to set up and run, need simpler equipment and are more forgiving for beginners. Saltwater fish-only tanks add salt mix, RO water, a refractometer and stronger flow. Reef tanks add high-output lighting, protein skimming and careful chemistry, and cost the most. Plan for the tank size the animals need as adults; bigger tanks are often more stable.
Freshwater, fish-only saltwater and reef tanks are three different hobbies in cost and effort.
Side by side
| Freshwater | Saltwater fish-only | Reef | |
|---|---|---|---|
| Startup equipment | Tank, filter, heater, light | Plus salt, RO water, refractometer, powerheads | Plus reef lighting, skimmer, dosing or reactors |
| Startup cost | Lowest | Moderate | Highest |
| Livestock prices | Low to moderate | Higher | Higher, corals extra |
| Water changes | Dechlorinated tap water | Mixed saltwater | Mixed saltwater |
| Testing | Ammonia, nitrite, nitrate, pH | Plus salinity | Plus alkalinity, calcium, magnesium, phosphate |
| Difficulty | Lower | Moderate | Highest |
Running costs
Electricity for heaters, lights and pumps, food, test reagents, filter media, and for saltwater, salt and RO water. Reefs add supplements and equipment upgrades.
Animal welfare
Research adult size and needs before buying any fish. Never keep animals in tanks too small for them as adults.
Filter it properly with our filter guide, and cycle before stocking with the nitrogen cycle guide. Browse tanks and filtration.
Common questions
Is a saltwater aquarium harder than freshwater?
It needs more equipment and closer attention to water chemistry, especially for reef tanks. Many beginners start with freshwater.
Why is a reef tank more expensive?
Corals need strong lighting, stable chemistry, skimming and flow, plus salt and RO water for every water change.
Do I need RO water for a saltwater tank?
It is strongly recommended, because tap water can contain phosphate, silicate and other contaminants.
Are small tanks easier for beginners?
Not usually. Larger volumes are more stable. A 20 to 40 gallon tank is a common starting size.