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Aquarium Builder

Plan compatible tank communities

Build a harmonious aquarium by selecting compatible fish species. Check temperament, water parameter requirements, tank size needs, and dietary compatibility to create a thriving underwater community.

f.care_level || f.temperament || f.min_tank_liters); }, addFish(slug) { if (!this.selected.includes(slug) && this.selected.length < 8) { this.selected.push(slug); } }, removeFish(slug) { this.selected = this.selected.filter(s => s !== slug); }, getFish(slug) { return this.fish.find(f => f.slug === slug); }, getCompat(slugA, slugB) { if (slugA === slugB) return {compatibility:'same', notes:''}; const entry = this.compatData.find(c => (c.fish_a__slug === slugA && c.fish_b__slug === slugB) || (c.fish_a__slug === slugB && c.fish_b__slug === slugA) ); return entry || {compatibility:'unknown', notes:'No compatibility data available'}; }, compatColor(level) { const map = { compatible: 'bg-emerald-100 text-emerald-800 dark:bg-emerald-900/40 dark:text-emerald-300', caution: 'bg-yellow-100 text-yellow-800 dark:bg-yellow-900/40 dark:text-yellow-300', incompatible: 'bg-red-100 text-red-800 dark:bg-red-900/40 dark:text-red-300', same: 'bg-slate-100 text-slate-500 dark:bg-slate-800 dark:text-slate-400', unknown: 'bg-slate-50 text-slate-400 dark:bg-slate-800/50 dark:text-slate-500', }; return map[level] || map.unknown; }, compatLabel(level) { const map = {compatible:'OK',caution:'Caution',incompatible:'No',same:'-',unknown:'?'}; return map[level] || '?'; }, get minTank() { let total = 0; this.selected.forEach(s => { const f = this.getFish(s); if (f && f.min_tank_liters) total += f.min_tank_liters; }); return total; }, get hasConflict() { for (let i = 0; i < this.selected.length; i++) { for (let j = i+1; j < this.selected.length; j++) { const c = this.getCompat(this.selected[i], this.selected[j]); if (c.compatibility === 'incompatible') return true; } } return false; } }">

Aquarium Builder

Warning: Incompatible fish detected! Tank Summary

Fish: | Min. tank: L

Add fish above to check compatibility and build your aquarium.

About Aquarium Builder

Build a harmonious aquarium by selecting compatible fish species. Check temperament, water parameter requirements, tank size needs, and dietary compatibility to create a thriving underwater community.

Aquarium Free Tool Interactive

Featured Fish

Angelfish

Pterophyllum scalare

Arapaima

Arapaima gigas

Atlantic Bluefin Tuna

Thunnus thynnus

Atlantic Cod

Gadus morhua

Atlantic Halibut

Hippoglossus hippoglossus

Atlantic Herring

Clupea harengus

Atlantic Sailfish

Istiophorus platypterus

Atlantic Salmon

Salmo salar

Barramundi

Lates calcarifer

Betta

Betta splendens

Black Crappie

Pomoxis nigromaculatus

Bluegill

Lepomis macrochirus

Blue Marlin

Makaira nigricans

Bonefish

Albula vulpes

Brook Trout

Salvelinus fontinalis

Brown Trout

Salmo trutta

Channel Catfish

Ictalurus punctatus

Cherry Barb

Puntius titteya

Chinook Salmon

Oncorhynchus tshawytscha

Clownfish

Amphiprion ocellaris
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How to Use

  1. 1
    Add fish to your community

    Search and select species you want in your tank. The builder shows each fish's temperament, size, and water needs.

  2. 2
    Check compatibility warnings

    Review alerts for aggression conflicts, pH or temperature mismatches, and minimum tank size requirements.

  3. 3
    Finalize your stocking plan

    Adjust species counts, review the combined bioload estimate, and confirm all water parameters overlap safely.

About

Building a successful aquarium community is an exercise in balancing biology, chemistry, and behavior. Every species you add brings its own requirements for water temperature, pH, hardness, swimming space, and social interaction, and the goal is to find a combination where every fish thrives rather than merely survives.

The Aquarium Builder approaches this challenge the way experienced aquarists do: by cross-referencing each candidate species against every other species already in the plan. For each pair, it checks temperament compatibility (peaceful, semi-aggressive, or aggressive), overlapping water parameter ranges, minimum tank volume, and dietary needs. Warnings appear immediately when a conflict is detected, whether that is a predator paired with a prey-sized tankmate, a tropical species mixed with a cold-water species, or a territorial cave-dweller doubled up without enough hiding spots. The builder also estimates the cumulative bioload of your selected community so you can gauge whether your filtration is sufficient before adding a single fish. Combined with the FishFYI species database, which provides detailed profiles for each species, the Aquarium Builder turns the complex art of community planning into a structured, conflict-aware process that helps both beginners and experienced hobbyists avoid costly and stressful mistakes.

FAQ

What makes two fish species incompatible?
Incompatibility usually stems from one of four factors: aggression (a territorial cichlid harassing a peaceful tetra), water parameter mismatch (an African rift lake fish needing pH 8.0 housed with an Amazonian species needing pH 6.5), size disparity (a large predator eating a small tankmate), or competition for the same niche (two bottom-dwelling species fighting over caves). The builder checks all four dimensions for every species pair you add.
How many fish can I keep in my tank?
Stocking density depends on filtration capacity, species bioload, and swimming behavior more than any single formula. The old one-inch-per-gallon rule is a rough starting point for small community fish but fails for large, messy species. A better approach is to stock conservatively, monitor ammonia and nitrite weekly for the first month, and add fish in small groups every two to three weeks to let the biological filter catch up.
Can I mix freshwater and saltwater fish?
No. Freshwater and saltwater fish have fundamentally different osmoregulation systems and cannot survive in each other's water. Brackish species (like mollies, gobies, and some puffers) tolerate a range of salinities but still require specific gravity within their tolerance band. The builder only suggests pairings within the same water type to prevent lethal mismatches.
What water parameters matter most for community tanks?
Temperature, pH, and general hardness (GH) are the three parameters that must overlap for all species in a community tank. Most tropical freshwater community fish thrive at 74 to 80 degrees Fahrenheit, pH 6.5 to 7.5, and moderate hardness. Keeping parameters stable matters more than hitting a perfect number -- sudden swings in pH or temperature stress fish far more than a slightly suboptimal but steady reading.
Should I add all fish at once or gradually?
Always add fish gradually, in groups of three to five, spaced at least two weeks apart. This gives the nitrogen cycle bacteria time to multiply and handle the increased ammonia load. Adding too many fish at once overwhelms the biological filter, causing an ammonia spike that can sicken or kill the entire community. Start with the hardiest, most peaceful species first and add sensitive or territorial fish last.