One inch of fish per 5 gallons ?

Either way, but the problem in counting sump/fuge is the event of a power outage. If that happens, your system is going to degrade VERY quickly if you were counting on sump/fuge, where as if you werent, you are fine as long as temp holds up.

I don't really consider a skimmer new technology. And, skimmers in reality do very little to oxygenate water, as the bubbles are not exposed to much of the water column at all. A simple airstone set-up in the sump will oxygenate the water much more effectively.

 

Well since i have a generator i feel compfy counting the fuge NOW if i didnt, i agree pack i would not count my fuge or sump.

 

(X)inches per (X)gallon rules are an anachronism. What mainly matters when planning a tank is the total surface area. The rule of thumb that I use is (allowed inches of fish)=(total surface area*)/40. Let's say my tank is 36L"x12W"x18H" (about 34 gallons). I, by this rule, can keep 10.8 inches of fish (36x12/48.) By the other rule (1" per 3gal,) I can have 11.22 inches of fish. That's about the same.

An aquarium that's the same volume but is 18x12x36 (LxWxH) can, w/ the per gallon standard, can have the same amount of fish as tank 1, even though it has 1/2 the surface area.

The thing that both of these is not taking into account is bioload. That varies from tank to tank. The amount of LR and LS should be taken into account. Also vodka dosing would make a larger bioload possible; but the beneficial bacteria also consume oxygen. Pretty much this is whenever access nutrients become a problem, that's too much. What a "problem" is varies varies from aquarium to aquarium. An ULNS, softie tank, or a FOWLR system would all have different ideas of what an okay nutrient level is.

*including all fuges and sumps

 

One of the benefits of a large sump is that you have a reserve of water to handle unexpected happenings. Yet, that same goal can also be accomplished without a sump by using only 1 fish in the display tank.

Or, you can use a sump (refugium whatever) to maximize your display tank fish load.

It's your choice depending on your goals. Thus, you could assume something in between 0 gallons and 295 gallons, depending on your goals.

 

'Rules of thumb' are based on 'technologies of thumb'.

How often is the water turned over? How much technology is used? How good is the technology used? How good is the circulation in the display? What's the highest water temperature? How many different avenues does oxygen have to get into the water? Is the homeowner a chain smoker? How much dissolved organics are in the water? And so on and on and on.

Any of these factors can affect the amount of oxygen in the water, or the quality of gas in the water, or affect how fast oxygen is replenished in the water.

This all ignores how much space the fish need to coexist.

Finally, how does one want one's tank to look? Pristine and ocean like? Or something else?

Final analysis: It's just a rule of thumb.

 

Here is the real question tho,

Would a batfish count as its length or its height?

 

LOL excellent!

And seriously, the activity levels and feeding requirements of the fish in the tank will have a significant effect too.