Large Sump (in comparision to tank size)

[Yulli]

So, I am getting a 150g from my grand father who passed away. I was thinking about making a sump for it, now he comes the crazy part. After some research I found a nice pond liner which is 7' by 10' for 30$ crazy right, now since its a sump and isolation tank i dont need to worry about being able to see in or anything like that. So in theory i could make a 280G sump, 76x21x41, internal dimensions since the liner should be able to fill that space along with overhang to secure to the wood. now if i place the overflow in the 150 a few inches below the water line ill need to leave space in case of power outage say 50g worth, which leaves me with a total water volume of ~370g. Question time, water changes should be done on overall volume correct? Now heres the other part lets assume i am going to put in relatively peaceful fish who don't generally have territorial aggression behavior problems, I should be able to "overstock" the tank, since its not really a 150 nor a 370 its somewhere in between?
Please point out any issues you guys see.

 

[markstrimaran]

I would say stock it, and water change it, based on the fish loading.
One guppy in 100 gallons will not require 50 percent water changed, weekly.

Put 1000 guppies in 100 gallons, you might find you need to change 75% weekly.

The add sump volume will allow a denser stocking. Asumming your tank is big enough for the fish to live in.

 

[esoxlucius]

You can't overstock your 150g tank with aggressive fish just because your overall volume is 300+ gallons. The fish aren't living in the open space of the 300+gallon total volume, they're living in the much smaller 150g part so aggression would still be an issue if you overstocked, unless you're planning on stocking some in your sump too!!! As regards water changes, you don't do water changes based on tank volume, you do them on nitrate levels, though granted, a larger overall tank volume will mean that nitrate will creep up more slowly, unless your madly overstocked.

 

[Yulli]

You can't overstock your 150g tank with aggressive fish just because your overall volume is 300+ gallons. The fish aren't living in the open space of the 300+gallon total volume, they're living in the much smaller 150g part so aggression would still be an issue if you overstocked, unless you're planning on stocking some in your sump too!!! As regards water changes, you don't do water changes based on tank volume, you do them on nitrate levels, though granted, a larger overall tank volume will mean that nitrate will creep up more slowly, unless your madly overstocked.

I dont plan on overstocking by much, it is more so for stability of NO3, there also not to aggressive. The sump will only have fish in the event that they need to be isolated for some reason, although i realize that medication will not be possible in that tank.

 

[BIG-G]

You could over stock as long as the fiah can live in a 150 and not kill each other. But would you really want to subject fish to beng over crowded and never being able to comfortably claim a space to do the things they do?
So I say the simple answer is yes, but to a resonable point. Depends on what fish and the space they need.