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6.3.3 THREE HOLE ARRANGEMENTS:
The three hole arrangement is nothing more than the above two combined, as the diagram clearly shows. Again a piece of pipe that has previously been perforated is used to create good water distribution behind all the corals and rocks.
Point and adjust the two water returns that are on either side of the tank in such a manner that the water is forcefully pushed towards the side panels of the tank, the short ends, and at a 45 degree angle upwards. This will push water out of the corners, move it upwards, and towards the outflow area that leads to the mechanical and biological filter.
Shown, but not to scale, are the three return holes, one on each side of the tank and one behind the coral and rock. Corner overflow box is shown in left back corner as well. See text for more details.
6.3.4 ADDING A CORNER OVERFLOW BOX:
A corner overflow box arrangement, of the type discussed earlier, can be added to any of the above water return arrangements. It can be positioned on the back left, on the back right, in the back middle of the, along the short sides of the tank, and so on. Where it is placed is not crucial. Mostly hobbyists will position it in the area where it interferes less with the aesthetic appearance of the tank.
Corner overflow boxes should be large enough to accommodate a good flow, but not so large that they look disproportionate in the tank. In smaller aquariums up to 70 gallons a box that is 3-1/2 x 3-1/2 is sufficient. The outflow hole should be 1-1/4 inch. On somewhat larger tanks the box should be 4-1/2 x 4-1/2. On tanks over 150 gallons the box can be made 5 by 5 or 6 by 6, or two boxes can be used, one on either side of the tank. Make sure when you do so that the tank is absolutely level. This will ensure an even flow through both corner overflow boxes.
Multiple corner overflow boxes can be used on larger aquariums. Two is more than enough. Usually, one is placed at the extreme left, and the other one at the extreme right of the tank, but there is no reason not to put them in a different pattern if you prefer, since their efficiency will not be affected by their location.
6.4 AQUARIUMS WITHOUT HOLES IN THE BOTTOM:
If no holes are drilled, the water needs to be brought down to the trickle filter by means of a siphon overflow, surface skimming arrangement. We discussed such devices earlier in this book. You may wish to reread that section if you are not clear about which type is best for the reef tank.
The water from the filter is returned to the aquarium by guiding the hose or hard pipe attached to your pump first back to the top of the tank, then over the tank and finally into the aquarium. You can split that line up, of course, and make it into two water returns. One from each end of the tank. All you will need to do so is a Tee fitting and some extra hose or pipe. Angle the returns in a manner that gives you as wide coverage of the whole tank as possible. Spray bars are not effective at doing this.
To the tank To the tank
|_________________________| | Flex or hard pipe
From filter sump
If these returns are submersed they can act as back-siphons. To prevent this you must install check valves in line. Use salt water safe ball checks or Y-checks, not flap checks. If not, a lot of water could siphon out of your aquarium during a power failure or when your pump stops because of failure. The more the end of the return is submersed, the more water could possibly back siphon. Keeping the returns out of the water completely will prevent all back siphoning, but will make it hard to adjust the water distribution inside the tank, and may also result in a lot of splash and salt creep.
Factor all these remarks into your thinking before you decide on which exact way you will plumb your water returns to the tank. If you are unsure talk to someone who has already installed such a tank, or discuss it with your local pet store or a manufacturer. Fluid mechanics in an aquarium are not difficult to understand, but someone familiar with them must, preferably, explain them to you.
6.5 CONCLUSION:
Good water flow and good water circulation are an absolute must in a reef tank. Do not overlook its importance. Acquire the best pump you can afford and protect it with a float switch, as explained in an earlier chapter.
All animals and most other lifeforms you keep in a reef tank are accustomed to strong water current. Provide it. You will be making the environment inside your tank closer than what they are used to in nature.
Such will benefit their well being and ensure that nutrients reach them as they should. Such will also make your tank look more realistic, especially if you use current alternating devices which will make the invertebrates sway from left to right, and vice-versa.
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