beginner's observation about water volume - your comments?

[guitarded]

it seems like we have general formula's based mostly on "per gallon". for instance, 1 fish per 5 gals, 5% to 10% water change per week, 1 cleaner crew member per gal, etc. anyway, you get the idea.

i am sure this is obvious to you folks, but it seems that much of the water volume is displaced by LR. in particular, i see posts that recommend that tangs should not be used in tanks 55 gals or smaller. i completely understand the reasoning, however, if a 75 gal tank has 40% of its water volume offset by LR and a 55 gal tank has only 10% of its volume offset by LR, then the 55 gal tank is, by far, more suitable than the 75 gal tank. this also goes for bio-load and other things, like heating wattage.

well anyway, even though this may be obvious, i notice that advice given doesn't normally factor this in. so would you folks agree that this is an important factor when making decisions? i am new so maybe i am just off base on this, but i am sure i will get a welcomed correction.

 

[jaiden]

LR is between 12 and 16 lb per gal. So if you have 100 lb in a 75, you have maybe 7 gal displaced. Less than 10% difference despite what it looks like. For your 75 to displace 40% of the tank it would be over 400 lb of rock.

You're not off base. It's a factor, but not a big one, and IMO most of these figures have already taken this into account. They're only ballparks anyway.

Also, it takes as much (or more) to heat a rock as to heat water, so that one is right out.

 

[indy]

You're a little off base in the 55 to 75 for a given fish figures. The recomended size isn't based on waste production that would affect water quality, so only losing 10% water instead of 40% doesn't apply. Your math is off, but I'm not talking math in this. It's based on the size and behavior of a given fish. You'll notice that some small fish have larger recomended tanks than some larger fish. This is because they need the extra room to feel comfortable and thereby remain healthy. Low activity fish of a given size can generally be well kept in a smaller tank than a high activity fish of the same size. Other recomendations are based on feeding, ie a dragonette. Not the most active, stays very small, but a large tank is needed to keep food production high enough that it can survive and thrive.

 

[guitarded]

yes, i understand. i know that bio-load is not the only thing we look at. that is why i mentioned a tang which needs swimming room. thanks for your explanations it really helps for beginners like me. i like to put out my thoughts so i can get the right perspective from experienced members.

 

[Phyl]

I was wondering the same thing when I was creating my fish list. I wasn't sure if I had to somehow back out the amount of rock I had from my total gallons. I was glad to find out that I didn't need to do that. Thanks for asking the question because I enjoyed the informative responses that you got.

Phyllis