Aquarium Stocking Calculator
Check if your aquarium is properly stocked. Find compatible fish, monitor bioload, and get schooling and temperament warnings. Free online tool.
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Betta Fish
Betta splendens
Neon Tetra
Paracheirodon innesi
Cardinal Tetra
Paracheirodon axelrodi
Guppy
Poecilia reticulata
Platy
Xiphophorus maculatus
Molly
Poecilia sphenops
Corydoras Catfish
Corydoras spp.
Bristlenose Pleco
Ancistrus spp.
Cherry Barb
Puntius titteya
Zebra Danio
Danio rerio
Harlequin Rasbora
Trigonostigma heteromorpha
Dwarf Gourami
Trichogaster lalius
Angelfish
Pterophyllum scalare
Needs 30+ gallon tank
German Blue Ram
Mikrogeophagus ramirezi
Kuhli Loach
Pangio kuhlii
Mystery Snail
Pomacea bridgesii
Nerite Snail
Neritina spp.
Cherry Shrimp
Neocaridina davidi
Amano Shrimp
Caridina multidentata
Otocinclus
Otocinclus spp.
Rummy Nose Tetra
Hemigrammus rhodostomus
Ember Tetra
Hyphessobrycon amandae
Pearl Gourami
Trichopodus leerii
Needs 30+ gallon tank
Swordtail
Xiphophorus hellerii
Endler's Livebearer
Poecilia wingei
Pygmy Corydoras
Corydoras pygmaeus
Clown Pleco
Panaqolus maccus
Hillstream Loach
Sewellia lineolata
White Cloud Minnow
Tanichthys albonubes
Pea Puffer
Carinotetraodon travancoricus
Honey Gourami
Trichogaster chuna
Celestial Pearl Danio
Danio margaritatus
Siamese Algae Eater
Crossocheilus oblongus
Needs 30+ gallon tank
Apistogramma
Apistogramma spp.
Sparkling Gourami
Trichopsis pumila
Recommended Filters for Your Tank
How It Works
This calculator assigns bioload points to each fish based on their adult size and waste production level (low = 2 pts/inch, medium = 4 pts/inch, high = 6 pts/inch). The total bioload is compared against your tank's capacity, which is your tank size in gallons multiplied by your filter's efficiency multiplier.
- Green (under 70%): Safe stocking level with room for growth
- Yellow (70-100%): Fully stocked, monitor water parameters closely
- Red (over 100%): Overstocked, high risk of ammonia spikes
The calculator also checks for temperament conflicts, temperature/pH mismatches, and schooling requirements to help you build a harmonious community.
Frequently Asked Questions
How many fish can I put in my aquarium?
It depends on the species, tank size, and filtration. The old "one inch of fish per gallon" rule is outdated and inaccurate. Our calculator uses bioload points that account for each species' actual waste production, adult size, and your filter type to give a much more accurate stocking level.
What is bioload and why does it matter?
Bioload is the total waste output of all living things in your tank. Fish produce ammonia through respiration and waste, which is toxic. Your biological filter converts ammonia to nitrite and then nitrate. If the bioload exceeds your filter's capacity, ammonia and nitrite will spike, harming or killing your fish.
Why do some fish need to be kept in schools?
Schooling fish like tetras, rasboras, and corydoras are social species that feel stressed and insecure when kept alone or in small numbers. Stress leads to weakened immune systems, loss of color, hiding behavior, and shorter lifespans. Always keep schooling fish in groups of 6 or more (8+ for some species).
Can I keep aggressive and peaceful fish together?
It is generally not recommended. Semi-aggressive fish like bettas and angelfish may harass, nip fins, or even kill peaceful tank mates. If you must mix temperaments, provide plenty of hiding spots, choose fast-moving peaceful fish, and have a backup plan to separate them.
Does my filter type affect how many fish I can keep?
Yes. A sponge filter provides less biological filtration capacity than a canister filter or sump. Our calculator adjusts the stocking capacity based on your filter type: sponge (0.8x), HOB (1.0x baseline), canister (1.2x), and sump (1.5x).