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Aquarium Stocking Level Calculator

Calculate your aquarium's stocking level and filtration capacity to ensure a healthy environment for your fish.

Tank Information

Enter the total volume of your aquarium in US gallons.
Enter the volume (or equivalent) your filter is rated for. If unsure, use your tank volume.

Fish Information

Enter details for up to three fish species you plan to keep.

Fish 1 Details

Expected adult length of the fish in inches.
Bioload Factor*
Low (e.g., Guppy), Medium (e.g., Tetra), High (e.g., Goldfish).

Fish 2 Details (Optional)

Expected adult length of the fish in inches.
Bioload Factor
Low (e.g., Guppy), Medium (e.g., Tetra), High (e.g., Goldfish).

Fish 3 Details (Optional)

Expected adult length of the fish in inches.
Bioload Factor
Low (e.g., Guppy), Medium (e.g., Tetra), High (e.g., Goldfish).

Calculation Results

Overall Stocking Level:

0%

Filtration Capacity Used:

0%

Warnings & Recommendations:

  • If your Filtration Capacity Used (0%) is greater than 100%, your filter may be a limiting factor. Consider upgrading or reducing bioload.
  • For each fish, if its Adult Size is greater than Tank Volume / 4, it may grow too large for your tank.

Overall Stocking Level Summary:

  • If your Overall Stocking Level (0%) is less than 70%: You are lightly stocked. You have room for more small, low-bioload fish.
  • If your Overall Stocking Level is between 70% and 100%: You are well-stocked. Monitor water parameters closely.
  • If your Overall Stocking Level is greater than 100%: You are overstocked. Consider reducing fish count or upgrading tank/filtration.
Made with Minform

How to calculate Aquarium stocking level calculator?

This calculator estimates your aquarium's stocking level and how much of your filter's capacity is being used based on tank volume and each fish's size and bioload.

Core formula: overall_stocking_level = (sum(adult_length_in_inches * bioload_factor) / tank_volume_gallons) * 100

Using the Aquarium stocking level calculator calculator: an example

Example values: 20‑gallon tank; Fish 1 = 2 in (Low bioload = 1); Fish 2 = 4 in (Medium bioload = 2).

Step-by-step calculation:

  • Compute each fish's stocking value: Fish 1 → 2 in × 1 = 2; Fish 2 → 4 in × 2 = 8.
  • Sum values: 2 + 8 = 10 (total_stocking_value).
  • Divide by tank volume: 10 ÷ 20 gal = 0.5 → overall_stocking_level = 0.5 × 100 = 50%.
  • Interpretation: 50% indicates a light-to-moderate stocking; check filtration similarly by dividing total_stocking_value by filter rated volume.

Frequently Asked Questions

What does bioload factor mean?

Bioload factor reflects how much waste a species produces; use Low for small, clean-water fish and High for messy, large species.

Should I use adult size or current size?

Always use expected adult length to avoid underestimating future space and filtration needs.

Can I replace one large fish with several small ones?

Possibly, but compare total_stocking_value and filtration load rather than fish count; many small fish can equal the bioload of one large fish.

When should I upgrade my filter?

Consider upgrading if filtration_capacity_used exceeds 100% or if you see persistent water-quality issues despite regular maintenance.


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