Originally Posted by Tihsho
The perk of the canister is that currently it's a 'free to you' situation which is always good. The canister running dry will inevitably either overheat the motor head or damage the impeller then you have that cost. Overall a sump is just cheaper to repair in the future. With the dimensions of the stand, plus the low flow you're probably after, you're just after a pump that has the head pressure to reach the height of the outlet. As for calculating the volume of water, that's easy. Just go through and measure your calcined area and do the following:
L x W x H = (cubic inches)/231= gallons
48" x 12" x 6" = 3456 cu in / 231 = 14.96 gallons
Obviously you will have displacement of the calcined media, but if you get that total volume in gallons + what ever your top off reservoir is you should be more than safe. In my example above, that 14.96 gallons + 5 gallon reservoir would be just shy of 20 gallons. So a 20 gallon long should provide more than enough space since the area calculated to be 14.96 gallons will have displacement due to media which will reduce the volume of water. ATO's are pretty reliable these days, so if the mechanical float switch is not giving you the warm and fuzzies, a simple electronic ATO with water level monitoring (around $100) will be more than safe. I've used some simple ones for years with no floods. Only floods I get are when I forget I'm filling a tank and walk away during a water change... Yay fishroom with concrete floors!
I'm not only recommending this to save a pump, but in actuality you're probably going to be away from home at some point. Say a vacation comes up. Having this knocked out now means one less thing you have to worry about/train the pet sitter to do when they swing by. Perk of the ATO res is you can also use it as the same res for your auto misting system. Win Win.
Also, let me add that whatever you're going to stock in there has a chance of producing offspring... Couple breeder boxes in the sump = simple way to raise tads without setting up a rack or table for cups before they sprout front legs.
I have no issues with the math but it gets a bit more complicated when you dump the calcined clay in. To be clear I am talking about taking calcined clay (think fine grain aquarium gravel) and putting somewhere between 40 lbs and 80 lbs into this tank. This will fill the bottom and make hills in the back. So yeah, definitely not going to have 14 gallons of water in this tank. If I can dump 3 gallons in there without overflowing I will consider it a big success. Another thing to consider is the water filled false bottom of this tank will not be rectangular. It will be triangular. I have a slanted false bottom and that slant changes angles as it gets closer to the front. The exact size and depth of all of this I haven't figured out yet. I cut some wood for a 45 degree angle and just shy of 4 inches wide but when I stack the pieces up it looks a bit small to me so I will need to redo it.
The good news is that 1) I don't have to make this decision now. I can set the whole thing up and see how much water it actually holds before making a decision. 2) No matter what I start out with I can always change it down the road. Nothing in the tank changes regardless of whether its a sump or canister filter, all of those changes happen in the stand so it won't be a big deal to swap one for the other.