Fish points


New Member
Aug 14, 2022
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This question is for the people of the UK. At pets at homes they have a system to that tells you how many fish you can have in a tank. The system is roughly 2 litres is 1 fish point and an inch of fish is a fish point. I have though for awile this system is flawed, but I want to know your opinions.


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Tank of the Month!
Jun 15, 2009
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East Yorks
It sounds like its loosely based on inch per gallon - which is actually on US gallons which are smaller than traditional imperial gallons. But they've made something they own, which is still weird as it mixes metric and imperial to make an arbitrary point system?

Inch per gallon is a good way of adding up numbers but it can make people think a 10 inch Oscar in a 10 gallon tank or 100 1 inch tetras in 100 gallons. When in reality the Oscar is obviously cruel and not going to work and the 100 tetras would probably be understocked.

Stocking a tank for it to thrive for years and keep the fish healthy for their natural lifespan take a lot of planning and there are lots of variables as you add different species.

Have you ever seen aqadvisor? Its a tank calculator, originally I didn't like it but its gotten a lot better over the years. Could be worth having a play with.



Fish Guru
Jan 26, 2008
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Perth, WA
I'm not in the UK but that type of measuring system is flawed from the onset. A small skinny fish like a 1 inch long neon tetra won't produce as much waste as a 1 inch long Oscar cichlid. If you have 12 neon tetras that are 1 inch long, that supposedly equals 12 inches of fish. But a single 12 inch Oscar will produce way more waste than 12 neon tetras.

There is no hard and fast rule about how many fish can go in a tank. There are numerous things that contribute to how many fish can be housed in any aquarium.

The following all contribute to how many fish can be kept in an aquarium.
How big the fish get.
How much food they get.
What type of food they get.
How often you do water changes.
How much water you change.
If there are plants in the tank.
If the fish are social and live in groups or on their own.
If the fish are peaceful.
How fast they swim, etc.


New Member
Jul 23, 2022
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These fish calculators are a load of baloney. All they do is confuse people and lead them into thinking that fish keeping is all about some kind of algorithm! lol. You can't beat good old common sense.

Some people have overstocked tanks, myself included, so what? Some people opt for the minimalist look. Whichever way you opt the fish police aren't gonna come knocking on your door.

The important thing if you choose to slightly overstock is to get a good handle on your nitrate creep and adjust your water changes accordingly to keep that water pristeen.

It just seems a load of nonsense to me that somebody somewhere can start giving recommended stocking levels for an aquarium, which is basically a puddle of water when, in the wild, the fish are in multi million/billion gallon environments. It's absurd.


Fish Herder
Oct 14, 2011
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Eastern Canada
Beyond dissing the stores, you can see they're trying to create a system to sell fish. One inch per gallon is okay for a fish built like a zebra danio. But once you start looking at fish that are 2 inches long, 1 inch tall and 3/4 of an inch wide, the hopelessness of the formula becomes obvious. No stocking system works as fish have different weight, different movement patterns and different needs.

1 inch per gallon stays around because it tells us what we want to hear. We always want more fish. In general, when we're new to this, we want many more than our tanks can properly hold.

If you step back and consider stores want to make money, and too many fish is profitable, you can see why they'd train their employees to use generous formulas! Overload a tank and you'll need extra equipment, medications, etc, and for a chain that doesn't survive on loyal customers, that's a dream.

I take whatever formula I get online or from common sense, and immediately cut it in half. I don't get invited to many fish parties with that approach, but if a stocking system says you can have 20 fish, get 10.

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