🐟 Fish Weight Calculator
Estimate aquarium fish weight using length-weight formulas by body type
| Body Type | a Value | b Value | Typical Species |
|---|
| Length (in) | Length (cm) | Est. Weight (oz) | Est. Weight (g) |
|---|
| Stage | Length Range | Weight Range | Notes |
|---|---|---|---|
| Fry | < 1 in / 2.5 cm | < 0.05 oz / 1.4 g | Recently hatched, fragile |
| Juvenile | 1–3 in / 2.5–7.6 cm | 0.05–0.4 oz / 1.4–11 g | Growing rapidly, developing color |
| Sub-Adult | 3–6 in / 7.6–15 cm | 0.4–3 oz / 11–85 g | Approaching mature size |
| Adult | > 6 in / 15 cm | > 3 oz / 85 g | Sexually mature, full color |
To estimate the weight of fish, you must consider several different things. When a fish starts to lose weight, it usually does not eat or does not get enough food. Also, inside parasites, old age or outside parasites can cause that.
Some fishes seem thin because of tuberculosis. It is possible to see that a fish looks very slim even though it was healthy recently. Some fishes puff up, as if they get fat after a big meal, but then look slim again the next day.
How to Weigh Fish and Tanks
That can make a fish look like a balloon before it loses weight again.
When you weigh a fish, it is good to use a scale with a built-in lip gripper. Simply attach it to the center of the bottom jaw. If the scale only has a hook, use separate lip grippers and set the weight to zero before.
For right values, attach the hook to the scale and lift the fish off the ground. It must be totally free. Even a little touch of a fin to a surface can change the weight.
Many types of fish grow over 50 lb or 22.7 kg. Big fishes can weigh more than 50 pounds. For example, adult ocean sunfish weigh from 247 to 1,000 kg.
The record weight for a pike is 43 pounds. Fishes keep growing as long as there is food and enough space.
Weight of an aquarium is also a big thing. Add fish and the weight of the tank goes up by physics. If you fill it to the top and it spills over when adding fish, you take away water and weight at the same time.
A 120 gallon aquarium is fine to start, but a bigger one can stress the floor. For weight problems, set the aquarium next to floor joists and against a load bearing wall. A fully stocked 55 gallon tank weighs around 600; 650 lbs.
A 75 gallon fully stocked tank has 850 lbs. An empty 25 inch tall 180 gallon tank weighs 338 lbs. To find total weight, add the weight of the empty tank, decorations, gravel, and water.
Water weighs about 8.3 lb per gallon. Most people use a safe amount of 10 lb per gallon for a full aquarium.
