As with any project, it’s always prudent to start out with a well laid plan. Designing a sump that is appropriate for your needs, yet meets the necessary requirements for proper operation is by far the hardest step in the construction process. Consider your specific design needs, and keep in mind the following rules of thumb.
• Build the sump as large as you can possibly accommodate. The larger the better.
• Consider all of your needs before you start building. Moving a baffle sucks!
• There must be enough excess space to house any water that drains out of the display, the plumbing and the skimmer, in the event of a power outage.
• Inlet chamber need only be large enough to house the inlet pipes and the skimmer.
• Bubble trap baffles should be 1” apart (or more)
• Refugium section should house at least 10% of the display tank’s total volume. (55g tank = 5.5g Refugium)
• Return section must house enough water to cover 24 hours of evaporative loss without exposing the return pump.
Our plans today will be to create a sump with refugium from a 20 gallon tank, to be installed onto an existing 29 gallon system. The sump will need to accommodate a hang-on mounted Coralife Super Skimmer 75, heater and a 650gph pressure rated pond pump for the return. In addition to the Skimmer (or inlet) section, refugium, and return section, we will also be including a bubble trap between the skimmer section and the refugium. I have created a diagram as a sort of blueprint for the project. This will help in ensuring that the sump will meet the requirements necessary for proper operation.
We’ll take a look at each section in the plans, and how they work out. As a quick note, planning out a sump requires calculation of water volume. The formula to Calculate water volume is: (Height x Width x Depth) / 231 = Volume in gallons (measurements are in inches)
Inlet (Skimmer) Section
Since the skimmers optional “hang on tank” feature will be used to mount the skimmer to the side of the sump, The inlet section need only be large enough to house the inlet pipes, and the skimmer’s pump and outlet tube. I chose to make this section a bit larger to allow easier access for cleaning. The final measurement was 5”.
Bubble Trap
Bubble trap baffles are designed at 1” apart. The larger the gap between baffles, the slower the water will flow through the bubble trap. A slower flow through the trap would ensure that even fewer micro bubbles from the inlet and skimmer made it through the trap, but I chose to reserve more space for the refugium.
Refugium
Standards suggest that a refugium should be no less that 10% of the total volume of the display. Since the display is a 29g aquarium, that requires our refugium to be at least 3 gallons. By calculation, that requires a minimum of 5 inches of width for the refugium. I wanted the refugium to be much larger than that, so calculations were made for the return section first. That left 11.5” available for the refugium, providing a much larger chamber of nearly 25% of the total display volume.
Return Section
The return section needed to house enough water to cover evaporation for 24 hours without exposing the pump. The return pump stands only 3” tall, so to be safe, the minimum water level will be marked at 4”. By calculation, a return section with a width of 5” would provide a capacity of 2.8 gallons. Respectively, 1 gallon would be needed to reach the minimum 4” mark. This would allow 1.8 gallons for daily evaporation. Since my 55 gallon system observes a maximum daily evaporation of 1.5 gallons, I figured it safe to assume that the 1.8 gallon capacity would suffice. As it turns out, the maximum daily evaporation of this system ended up being just about 1 gallon per day, so my assumptions were correct (thank goodness).
The last thing I needed to consider before moving forward was if there was enough spare room in the sump to cover the drainage from the display and the plumbing in the event of a power outage. I calculated the amount that would drain out of the display tank would be about ¾ of a gallon. I conservatively estimated that the plumbing held less than ½ of a gallon. Therefore, in the event of a power outage, I would observe a 1” increase in the water level within the sump. This design provides an extra 3” of space above the highest water level during operation, which is more than enough to house the extra water.