How many fish for my 40 gallons tank?

Ratios can be useful when properly applied--and that often isn't the case. It's a matter of being aware that the ratio does not take into account behavior, and only applies to certain fish (rather, a ratio is valid for fish that are similar size/shape, but different ratios must be used for different shapes/sizes)--something few newbies will research far enough to discover. In this case, it's not the bio-load of the fish in question that's a concern--it's the behavior. The behavior of damsels (clowns are in the damsel family) is such that they need much more space than their body size dictates. I disagree with your math, as well--percs get to 2 inches, so that's 6 inches, a bicolor or flame can easily hit 5 inches, the royal gamma at least 3 inches, and an inch each for the gobies (and Catalina'a are cold water fish, seldom survive long in a tropical setup), giving a total of 15 inches. Of course, you're dealing with hugely varying bio-mass--a healthy bicolor will mass much more than 5-7 gobies--which is why length based ratios are not very valuable when the same ratio is used for multiple species.

Further--this tank sounds fairly new, with minimal boilogical filtration, meaning a slower addition of fish should be followed anyway.
 
I agree with Orion, and if there is anything else in the tank a ratio will also not work, or be off... (i.e. what if there was 90lbs of live rock, or how about 6" dsb... ratios are fine if you want to say how much light you think some clam should have, or even 10x turn over per hour for current or x watts per gallon for a heater).

Ratios are one of the best tools that beginners can use to get a good start on a complicated and expensive hobby.
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Ratios do work for many things in the hobby, I don't think it does for how many fish you can have in a tank based on their length though.
 
I think ratio is actually better for an experienced hobbiest. I new person doesn't know how big, and what kind of waste a fish is going to create. So they need to research instead of just using math- or use both.
I think for damsels you can use this method, except for territory. Orion girl was so right, about the fish Baybay wants to keep.
A good example is a lion fish. Even giving him 3:1'', you couldn't put a 10'' Lion into a 30 gallon. He might be okay if he grew up in there, letting the bio grow, but he would be swimming in waste! To make the tank look okay you would have to change water every other day. And he woul not be able to swim around happy.
But in the same tank you could put five damsels and they could get 2-3'' and they would be fine. It's like comparing apples to oranges.
Maybe if Baybay would of added them all at once there would be a better chance of just one being agressive keeping the rest in line, (that's just what happen in my tank)
but now adding them is going to cause WWIII in the tank.

Likes to ramble-Tina
 
OrionGirl said:
(and Catalina'a are cold water fish, seldom survive long in a tropical setup)
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15 years ago I would have agreed with this (I tried it, and you are right), but Catalinas are now being tank raised, and as I understand it, they are easily adaptable to tropical temperatures.

I know they were hard to find for quite a while a few years back, and that's probably why. I love these little guys, and I will be trying a tank raised sample soon.
 
OrionGirl said:
I disagree with your math, as well--percs get to 2 inches, so that's 6 inches, a bicolor or flame can easily hit 5 inches, the royal gamma at least 3 inches, and an inch each for the gobies, giving a total of 15 inches.
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OK, let's use your numbers. Even adding another Goby, you'd have 16 inches, or a ratio of .4. Still within acceptable limits with proper filtration. I wouldn't do this with live rock and live sand, but a good wet/dry system would handle it.

Of course I agree that compatability will still be the final test. There are all kinds of compatability charts out there and a little research will get you started, but compatability is actually a bigger variable than size. I once had an Undulated trigger (probably the meanest fish by reputation out there) in a tank with a variety of other fish and he got along with everyone. Go figure!

All I'm saying is that you have to have a starting point. Ratios, compatability charts, books and forums all help. However, as we all know, nothing is for certain, and you just have to give it a try.
 
Please share with use about the Catalina's--I've tried them within the past 4 years with dismal results--I'd be interested if they can thrive in warmer temps.

Agree--ratios are a good starting point, but they can't be the deciding factor, IMO.
 
BayBay,
as you can see, everyone has done there own research and they have there own mystakes and successes with experience. Just take it all in and find what makes since to you and try it.
You have a good start to getting info here, everyone on here gives awesome advice!!!! (even if we don't all agree)
The only way you can really know what work is jump in. Sometimes you will find out you can go totally against the "rules", ans still have success.
Everyone told me, when I first started my fresh water that I could only have 5 fish in my ten gallon. Believe it or not I had 15!! And they all lived a long time.


Likes to ramble-Tina
 
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