Designing A Marine Tank

[xxBarneyxx]

Still looking into places to get my big marine tank from and after going to World of fishes (great store btw, the guy there I spoke to there, Andy, was very helpful) they will build a tank to your specifications.

The basic dimentions of the tank will be 5ftX2ftX2ft and I plan on using a tunze wavebox for the main water movement.

As such I think the best place to put the weir would be in the center of the tank as the water on the sides of the tank can apprently rise and fall by up to 2 inches with a wavebox (while the center should stay at pretty much the same level).

The question is what size should the weir be? is there any sort of "rules" as to the ideal size of a weir? I was planning on just have two holes drilled, one for the overflow and one for the return pipe.

If I'm going to get one built from scratch is there anything that would be a really good idea to add? I'm thinking that I might have it slightly over 2ft tall so that when the hood surround is on it covers up the rising and falling water level (so something like 2.5ft with the surround cover the top 1/2ft of tank).

 

[SkiFletch]

What flowrate through the sump are you considering? Typically you're talkin 5 times the tank volume. Once you calculate the florate you're trying to achieve, then you can calculate the weir length and the bulkhead ID

 

[xxBarneyxx]

Thanks, I knew there must be some sort of method of working it out.

Given a X5 flow rate through the sump this equates to around 2800LPH (500GPH US give or take a gallon or two). Given head loss and differences between actual performance and listed performance this should mean a 3000LPH return pump should be just about right.

If you can point me in the direction of how to calculate it all from this that would be great!

 

[SkiFletch]

Thanks, I knew there must be some sort of method of working it out.

Given a X5 flow rate through the sump this equates to around 2800LPH (500GPH US give or take a gallon or two). Given head loss and differences between actual performance and listed performance this should mean a 3000LPH return pump should be just about right.

If you can point me in the direction of how to calculate it all from this that would be great!

Sure, I'll PM them to you tonight. Remember though, flowrate losses due to head pressure increases are often bigger than you're assuming. To get 2800LPH through the sump, you're prolly talkin at LEAST a 3500LPH pump. Remember, head loss for most tanks with sumps under the tank is gonna be somewhere around 5ft (1.5m). Then what you have to do is get the pump curve for your pump of choice and see what the flowrate is at that headloss. Sometimes the curves are relatively linear, but sometimes they're not. You can be really far off if they're not linear . Usually if the head pressure is really high but the flowrate is low, the curve is very steep; meaning increased headpressure has little effect on flowrate. If the head pressure is really low and the flowrate really high, the curve is very shallow; meaning increased headpressure has LOTS of effect on flowrate. Its important to know your curve, cause the last thing you want is to order the pump, choose your bulkhead size, drill the tank, and find out its pushing too much water for the overflow to handle...

Anyways, calculators later tonight, enjoy them when you wake up in the morning