Determining Stocking Levels

[Bugdozer]

Most of us have seen the classic "inches of fish" rule for stocking our tanks, also many of us will have encountered the "filter based" guidelines as well, which of course conflicts with the inches of fish idea.
Which made me curious to investigate: What actually determines the safe stocking level?
Obviously overcrowding in terms of personal space per fish (which will be species dependent) and the ability of the filter to remove waste products from the water (dependent on total water volume, filter throughput, amount of crap emitted by inhabitants and tolerance of species to buildup of ammonia and nitrite.)

So let's standardise things to make an example: you have a 100 litre tank, no live plants, and a filter that is able to pump 300 litres per hour. Tank temperature is 25C, pH is 7. What is the "correct" number of adult neon tetras that can be added?

 

[N0body Of The Goat]

I'd be worried if the filter is only turning over the water just 3x an hour, presuming the filter was really rated higher and you have allowed for the minimum 10% drop off in real world use. Even for Neon Tetras, I'd want a real world 6x turnover.

If Neons were the only fish, I would not want to be keep ing them permanently at 25C, they are more of a sub-tropical species (which is why Cardinals are often suggested at higher temps). I'd be keeping them at 22C.

With the adjustments above, I'd aim for ~15 Neons.

...Roll on the "tardis" stocking plans!

 

[Bugdozer]

It's a thought experiment. It's not the real world. What the filter is "rated for" is irrelevant, I'm telling you what it does in this scenario. The temperature is what it is (three different sites - including this forum's species index - list 26C as the top temperature for neons), the fish are neons in this example. If I'd used cardinals you'd probably have told me to use a different pH or something. So no adjustments, the parameters are what I say even if they're not ideal, so without your adjustments, is 15 still your top number?

BTW this scenario will be followed by a similar one with some slightly different parameters, which is why you have to go with what's given for this first example.

 

[creeker]

The dimensions of the tank would be as or more important than just the capacity. A 100 liter "tall" tank would hold less than a 100 liter "long" tank.

 

[Tizer]

I'd stuff 50 in it Then transfer them to my larger tank later on and have my Firemouth eat them all.....oh wait....i've already done that.

 

[tomtomtom1230]

It's a thought experiment. It's not the real world. What the filter is "rated for" is irrelevant, I'm telling you what it does in this scenario. The temperature is what it is (three different sites - including this forum's species index - list 26C as the top temperature for neons), the fish are neons in this example. If I'd used cardinals you'd probably have told me to use a different pH or something. So no adjustments, the parameters are what I say even if they're not ideal, so without your adjustments, is 15 still your top number?

BTW this scenario will be followed by a similar one with some slightly different parameters, which is why you have to go with what's given for this first example.

I don't think it's irrelevant at all since you're trying to determine and I suspect collaborate both methods of stock determination to come up with a more accurate way of safely stocking an aquarium. In this scenario I would be worried about under filtration therefore limiting your stocking maximum. I have a 120 litre tank and I aimed for at least 500lph (this is still considered under filtration). It turns out my filter is actually about 750 litres per hour which is acceptable I suppose.

When stocking a tank I try and base it upon both filtration and a bit of common sense. ie: if it looks crowded then chances are that it probably is. If the fish have a restricted space to move around in, this'll shorten their lifespan drastically and they won't be as healthy as they could be since their muscle development will probably be impaired. I think most people opt for the 'suck it and see' method whereby they add a few, do some water tests and if there's nothing amiss then add a few more, do some more water tests etc until they consider themselves fully stocked.

In the given scenario, I would probably stock no more than 12 - 15 neons. If the filtration was upped to approximately 5-600lph then I would consider probably adding around 20 - 25 neons. Another limiting factor though, as mentioned, is the dimensions of the tank. If it was a longer and less cuboid shaped tank then the previous statement stands. If however, the tank was a taller style then I'd reduce the number of neons to about 15 - 18 purely for piece of mind over oxygen levels.

 

[Ruskull]

I'd stuff 50 in it Then transfer them to my larger tank later on and have my Firemouth eat them all.....oh wait....i've already done that.

Bad Tizer, bad..............

 

[Bugdozer]

It's a thought experiment. It's not the real world. What the filter is "rated for" is irrelevant, I'm telling you what it does in this scenario. The temperature is what it is (three different sites - including this forum's species index - list 26C as the top temperature for neons), the fish are neons in this example. If I'd used cardinals you'd probably have told me to use a different pH or something. So no adjustments, the parameters are what I say even if they're not ideal, so without your adjustments, is 15 still your top number?

BTW this scenario will be followed by a similar one with some slightly different parameters, which is why you have to go with what's given for this first example.

I don't think it's irrelevant at all since you're trying to determine and I suspect collaborate both methods of stock determination to come up with a more accurate way of safely stocking an aquarium. In this scenario I would be worried about under filtration therefore limiting your stocking maximum. I have a 120 litre tank and I aimed for at least 500lph (this is still considered under filtration). It turns out my filter is actually about 750 litres per hour which is acceptable I suppose.

When stocking a tank I try and base it upon both filtration and a bit of common sense. ie: if it looks crowded then chances are that it probably is. If the fish have a restricted space to move around in, this'll shorten their lifespan drastically and they won't be as healthy as they could be since their muscle development will probably be impaired. I think most people opt for the 'suck it and see' method whereby they add a few, do some water tests and if there's nothing amiss then add a few more, do some more water tests etc until they consider themselves fully stocked.

In the given scenario, I would probably stock no more than 12 - 15 neons. If the filtration was upped to approximately 5-600lph then I would consider probably adding around 20 - 25 neons. Another limiting factor though, as mentioned, is the dimensions of the tank. If it was a longer and less cuboid shaped tank then the previous statement stands. If however, the tank was a taller style then I'd reduce the number of neons to about 15 - 18 purely for piece of mind over oxygen levels.

Jeez, you people are obsessed with trying to second guess me! I'm not trying to come up with a more accurate method of stocking an aquarium. I don't have a 100 litre tank, my filter system is more efficient than that, and I don't keep neon tetras. Neither is my pH 7, although my water temperature is indeed 25C.

Regarding the shape, the tank is a sphere and it magically has perfectly oxygenated water at all times. If you want to know the maximum diameter of the tank, it's a simple matter of applying the correct formula (the volume is 4/3 of pi multiplied by the radius cubed, so take 100 litres, express it as cubic centimetres, divide that number by four and multiply it by three, divide that by pi and find the cube root of the result. Then double it. That's the diameter in centimetres.)
Anyway, thankyou for your assessment of the number of fish.

 

[tomtomtom1230]

I wasn't trying to second guess you at all. There are simply too many variables (in my opinion) to give a completely accurate way of stocking a tank, especially without it being right in front of one to see for one's self. The question you asked (ie: what actually determines the safe stocking level) is the result of all of those variables divided by pi No offense meant.

 

[fluttermoth]

tomtom is right, there are too many variables to be able to give a definitive answer.

Just for one instance, a person with high nitrate in their tap water won't be able to stock as heavily as someone with very low nitrate.

Then, also, filtration isn't just about how many times an hour it turns the water over, but also about how efficient the media is and how large a surface area it has for bacterial growth.

Then there's the amount of plants, surface area and a hundred and one other things that would make a difference.

This is, of course, why advising on stocking can be so hard and why it is an art as well as a science.

 

[Bugdozer]

I wasn't trying to second guess you at all. There are simply too many variables (in my opinion) to give a completely accurate way of stocking a tank, especially without it being right in front of one to see for one's self. The question you asked (ie: what actually determines the safe stocking level) is the result of all of those variables divided by pi No offense meant.

Yes, this is why I'm using a simplified, standard example. I understand that in the real world it's more complex. I intended the example to be treated as if any parameter that wasn't mentioned could be considered irrelevant, even though in the real world it can't.
Regarding tank shape: this is again a species dependent issue. Some fish barely move and others like to race long distances. Hence my use of one species in the example. However, while the volume of the tank is relevant in terms of dilution of fish waste, and also for percentage water turnover by the filter, the shape of the tank affects neither of these factors. It only affects the personal space aspect of the fish and their room to swim, and the oxygenation.
What I'm trying to work out is how these factors balance against each other for a given species, because it should be possible to graph them against each other to find an optimum value for both.
Stocking is only an art if the variables are taken all together in a big mishmash. I believe if we approach every variable individually and factor in how relevant it is in the overall scheme of things, it can become a science. That's why we need to approach this with a very simplified starting point. Once the effects of volume and filtration are established, then one can move on to things like nitrate content, non-filter bacterial area and so on.

 

[Tolak]

Having seen 1000 & 1200 in a 125 gallon I'd stock a little more conservatively & try to keep it under 100 in that tank.

 

[JohnDyer]

1000 Neon Tetras in a 125 gallon tank? That seems slightly ridiculous Even with nothing else in the tank, it would look crowded
For the purpose of your survey, I'd say 12-18.

 

[Tolak]

What actually determines the safe stocking level?

And that's just my point, it's all a personal issue of being able to work with and around the stocking desired. Each situation is individual, you can't do a cookie cutter stocking that will apply to all. You'd want at least 8 in that tank, the upper range is the individual's call. Personally I wouldn't hesitate to put 50 in a 100 liter, depending on tank dimensions probably more.

 

[Staxx]

i think what tolak is trying to say. your stocking is determined by how much work your prepared to put in.

like water changes and so on to keep the stock healthy.