Trying to determine how big to make my bog

[Mmathis]

OK, no passing judgement — I admit that I am math-challenged.

To determine the size for a bog [I have goldfish], the general consensus is that the bog should be about 30% of the total surface area of the pond. Does that mean....the entire volume of the bog [including gravel] should be 30%? Or does that mean the surface area of the bog should be 30%?

I have always intended to add a bog to the pond so I can do away with the Skippy. I am trying to decide whether to dig the bog, or use a 300 gal stock tank that I already have. Using the tank would be the easiest solution, but at 300 gal, it’s probably right at the limit for an effective bog [I need to get a current measurement of the pond, but I think its SA is around 300]. And I would rather have the bog be a little larger than necessary. I don’t want to haul and plant gravel, only to realize that I made the bog too darn small!

As an FYI, there is also what I call my “turtle-bog” that feeds the pond. It’s about 600 gal, but only about 1/2 of it is planted, as the other 1/2 is a watering hole for my turtles.

 

[RobAmy]

Surface area to surface area is my understanding. Not volume

 

[Telion]

Thats been my understanding too but I can understand the question especially if you consider the depth of one vs the other. They could vary greatly and if they do should you increase the surface are for a deeper pond? Going too deep might not be as much of a benefit as the roots of plants only go so deep. At that point its more like mechanical filtration as it filters up through the rocks.

 

[GBBUDD]

The only benefit I can see to a deeper bog is to allow for the sediment fish waste / pollen / buds decaying matter the finer particles flush into the bottom of the bog and have a chance to settle before they are forced up into the rock thus preventing clogging. This is the theory of hydroponics as I have gathered let the plants get the nutrients from the water not the soil.

If your pond is doing well now the addition of a bog probably won't hurt at any size unless there is not enough waste/ nutrients and the plants starve