no such thing as 'rule of thumb'?

[nightlife20]

In case you haven't heard, there is this stupid "rule of thumb" in the aquarium hobby that you can keep 1 cm of fish for every 2 liters (1 inch per gallon) of water. Let me start by explaining why that rule should be ignored completely.

Consider a 3 cm (1 in.) Neon Tetra and a 3 cm Goldfish. In terms of waste produced and body mass, it will take about 20 Neons to equal that 1 Goldfish. Also consider a 3 cm Pink Kissing Gourami. The Pink Kisser is just a baby while the Neon is an adult already. That Kisser has a much higher metabolism and therefore will eat more and produce more waste. Also, the Kisser has much more body mass than a Neon. The cm/liter (in./gal.) rule is meant to apply to small fish at their adult size, such as Neons, Cherry Barbs, Cardinal Tetras, White Clouds, and Zebra Danios. Do NOT use this rule for any fish which is bigger than a Neon. Not even for a Platy or a Swordtail.

Now that you can see what I'm talking about, let me explain how many fish you can comfortably fit into your tank. The most important consideration is that you are doing regular water changes and have the appropriate biological filter for your tank size. Provided you are doing the appropriate maintenance and have the correct sized filter, then you will probably never have problems with water quality, regardless of how many fish you put in the tank.

The important considerations are aggression and swimming space. You should never put a fast swimming schooling fish in an aquarium smaller than 200 liters. (See the chart below). Many hobbyists assume that they are losing fish mysteriously because the tank is "overcrowded." In reality they are just not giving the fish the appropriate swimming space. When packed into a small tank, "fin nippers" will become very territorial and create stress on your other fish. This is what is resulting in the mysterious fish loss. And it is not related to water quality.

OK, so how many fish? To be honest, there is not a limit. As long as you are putting the fish in the appropriate size aquarium, you will be content with the fish load long before you have reached the biological limits of the tank. I have kept 40 liter aquariums with 30 fish and 200 liter aquariums with 100 fish. The catch is to provide the correct maintenance and be smart about what fish you mix together. Just watch your tank. When your tank starts to look crowded then stop adding fish. There really is no "rule of thumb" for adding fish. This depends entirely on the mix of fish you choose. Good luck!

Mark 'Ffishmaster' Lehr
Read other fine articles by this author at
Ffishmaster´s Website

is this a good thing to be reading?

iv always been told about the 'rule of thumb' and most fish keepers go by this rule... but some points are hard to disagree with...


discuss........

 

[tstenback]

Just as with any statistical type of information you can play the numbers any way you want to make your point of view seem like the right one, or even a possible one. What if i had an oscar in a 100 gallon tank, big enough for the oscar ,right? Now then according to this article i could add 10 more oscars to the tank. 100 gallons is big enough for one oscar therefore it is big enough for each oscar, right? there is enough space for swimming around(for each oscar) therefore this would be fine. I dont know if you could possibly keep up with the maintenance to make this work but according to the article with proper water changes it should. I don't agree with the authors statement in theory or practicality and it ceertainly should never be advice to novice fishkeepers. IMO

 

[Tempestuousfury]

However, the author states that the rule shuldn't apply, and that's true.

Aggression and space are major concerns. If you can follow the procedure, great, but the only way you can fin balance is through experimentation and educated speculation.

 

[tstenback]

However, the author states that the rule shuldn't apply, and that's true

I agree with this but only for those with the water and species knowledge to ensure it can be done safely. A rule of thumb is not set in stone it is merely a guideline and a good one for most fishkeepers.

 

[thecichlidaddict]

I've always said this, and always will. There are no rules of thumb. Every situation is unique and should be considered so. Forums like this are such a great way for people to figure out what they need to know based on their own setup and situation.

Any rule of thumb, as far as I'm concerned, is wrong.

 

[clutterydrawer]

I agree with the fact that an inch of tetra in no way equates to an inch of goldfish or gourami or catfish or whatever. but i think its courting danger to include the sentence "OK, so how many fish? To be honest, there is not a limit." because a lot of people who are totally new to the hobby are gonna read that, think "great i can do what i want" and terrible things will ensue. especially if they dont take in the rest of the article properly which is easily possible.

 

[pendragon]

I'm sorry, but this is an area where we just have to disagree.

"Rules of thumb" are important because they set guidelines for beginners, if for no other reason. This singular fact is all-important; to wave it away as nonsense is just foolish. With proper experience and knowledge, a rule of thumb becomes less constraining for you, as it is meant to. If you are an expert fishkleeper, ignore them, but don't tell everyone else they should, too. Giving everyone a license to disregard traditional wisdom and provide a healthy environment for their fish based on their personal judgement is just naive and irresponsible. Not everyone has the wealth of experience, skill, and resources to draw from as you. If you feel your skill qualifies you to make unorthodox decisions that may affect the health of your aquarium, then by all means ,do so - but don't condemn traditional wisdom to the uninformed lurker who may have just used your post to justify the forty-five neons he just put in his new ten-gallon tank. After all, in his judgement, they'll be fine and happy.

There are times rules of thumb are meant to be broken, and times they are meant to be followed. If one has not the wisdom to know which from which, they let it be. The problem is that all people tend to consistently overestimate their wisdom.

pendragon!

 

[nightlife20]

*coughs into hand* if u look u will see i never wrote this peice of information... I said there were bits i could agree to....

 

[Tempestuousfury]

Same here. There's some good information there, but there has to be a limit to the number of fish you put in in order to reduce stress and reach an equilibrium.

 

[CFC]

pendragon just about summed it up


The "rules of thumb" are good starting guides for new fish keepers and will help to stop them making huge mistakes, as your knowlege grows you can decide for yourself how many fish your tank can hold.

 

[Stryker]

A rule of thumb is just that..... and as said above its better than nothing for beginners. But in some applications it is rediculous.... but of course, no one rule could ever apply to such a dynamic hobby.... which is why when I see people setting about others over the rule of thumb as if only to prove they know something really makes my blood boil.

As an afterthought, I do agree with pendragon that trying to discredit the rule of thumb is stupid and thoughtless and as far as I see, also again I see those words as just someone who feels they have to prove they know something.

 

[Cheese Specialist]

I have never gone on a rule of thumb. I go on parameters and how much room the fish look to have. It's ok IMO to have more fish if (parameters permitting) some are active only at night when others are sleeping.

I tell newbies about rules of thumb but I also say what I think.

 

[Tempestuousfury]

I've noticed many people prattle about rules of thumb as though they are the answers to everything. Yet when these poeple are told they are wrong, it doesn't change anything.

Anyways, you could add a poll and ask whether people follow them. Those who do should get a chance to state why (or be forced to do so ).

 

[Cheese Specialist]

Anyways, you could add a poll and ask whether people follow them. Those who do should get a chance to state why (or be forced to do so ).

I know lots of people who go on about rules but I know of very few people who use them!!!

 

[thecichlidaddict]

As an afterthought, I do agree with pendragon that trying to discredit the rule of thumb is stupid and thoughtless and as far as I see, also again I see those words as just someone who feels they have to prove they know something.

Hmm.. I see it as giving the beginner the benefit of the doubt that they can understand why rules of thumb don't apply once it's explained to them.