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by Dr_DBW
Surface skimming of the water from the main display tank of a reef system is advantageous. It allows more efficient removal of surface active compounds to the sump, and hence the skimmer. This function is explicitly obvious when you compare the appearence of the water surface between a tank that has a surface skimmer and one that doesn't.
The typical manner in achieving this is to have a weir on the end or corner of a tank. But in the case of a tank that has just a standpipe (which some people want if it is a 360o view tank and insufficient space for a weir in the center), it may be difficult to do this. Well, there is a rather simple manner is still getting a decent flow through the standpipe, with efficient surface skimming. All it involves is increasing the standpipe diameter just below the water surface, as shown in the below diagram.
Basic design of the standpipe weir/overflow.
I assisted in setting up a couple of tanks using this method and it does work very well. Slotting the top of the pipe will also help to keep various critters going over into the standpipe. There can be some issues with gurgling, depending on the diameter of piping used and the water flow through it, but this is easily solved by placing some airline (or a slightly larger diameter vinyl tubing, around 5-10 mm) down the standpipe to around half way or the base. That then allows the air to still enter and mix with the water flow, but eliminates the gurgling noise.
Something similar can also be applied if the tank is drilled towards the top of the sides. Below is something like what can be done when it is very close to the top of the tank. The only problem can be sealing around where the piping goes through the side of the larger diameter piping. But with a very tight fit and some PVC solvent you can get a nice water tight seal. Using something like Weldon 40 would be a good idea as well, which will bond to PVC. When things are lower, then use the former design, but just have an elbow in the 25 mm section of piping, much easier to set up that way.
Standpipe weir/overflow design when the bulkhead goes through the side of the tank close to the top.
Examples
Here are some photographs of a fellow Aussie that has used this principle on their tank. It is working well and they have used a sloped reducer fitting that will mean there will be no waterfall type of noises.
Parts laid out ready for assembly to make the standpipe weir.
Combined standpipe/weir using a reducer fitting.
Top view of the standpipe weir in operation.
View from the front of the tank of the standpipe weir installed and in operationg.
If you happen to set one of these up, would be great if you could send me an image of it. Only registered users can write comments.
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