Freshwater 20-gallon: $10-25/month. Freshwater 75-gallon planted: $30-60/month. Saltwater 30-gallon nano: $50-100/month. Saltwater 75-gallon mixed reef: $80-150/month. Saltwater 180-gallon SPS: $150-350/month. Costs include electricity, salt mix (saltwater), supplements, food, filter media, and fish/coral attrition.
Monthly aquarium costs are dramatically higher than most beginners expect. Equipment is one-time; operating cost is forever.
| Cost line | FW 20gal | FW 75gal | SW 30gal nano | SW 75gal reef |
|---|---|---|---|---|
| Electricity | $5-10 | $15-30 | $15-30 | $25-60 |
| Food | $3-8 | $10-20 | $10-20 | $15-30 |
| Filter media | $2-5 | $5-15 | $5-15 | $10-25 |
| Salt mix | - | - | $10-25 | $20-50 |
| Supplements / dosing | - | - | $10-25 | $15-40 |
| Total monthly | $10-25 | $30-60 | $50-100 | $80-150 |
Excluded: livestock attrition (replacement of dead fish/coral), one-time equipment failures, and any added inventory (new fish, new coral). Plan for $20-50/month additional in livestock spending if you're actively building the tank.
Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.
Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.
Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.
Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.
Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.
How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.
What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.
How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.
Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.
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