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INNOVATIONS IN TANK DESIGN:
The Cascade System

by Bill "Pegasus NZ" of New Zealand

The Cascade Conversion. Using this system, water has to flow from a tank at a higher level, to one at a lower level, and then back again.

Cascade system set up for three tanks

This is nothing new of course, and has been done many times before using different methods, many of which need the tank to be drilled in some manner, or reliance on a siphoning system, both of which can cause problems. If you are unconcerned about passing water from one tank to the next, then the cascade system is an ideal way to use a single heat source to heat a number of tanks. I used the following because I have just set up a large number of 2'x15"x12" tanks and needed a cheaper method of heating them. The application here will need one of the end panels on the tank to be made, or altered, to suit, so a little skill in glass cutting is required. It is also mainly aimed at those that are making tanks, although you could convert an existing tank if you were brave enough.

One letdown, if it is such a thing, is that each additional tank has to be slightly higher than the preceding one, a height of only 30mm (1"). It may not suit everyone's taste, but for my application I was unconcerned and used a single flat stand with a 30mm packing under each additional tank.  Any number of tanks can be added, provided the next one is slightly higher than the last, but it is suggested that only up to five or six are connected at this stage, or you can do it with just two tanks if you want to experiment.

The end glass at one end is cut 30mm shorter than the tank top. The piece you removed will now become part of the end piece, but will need cutting to suit and then siliconing into position. For the actual overflow I used a short rectangular tube. My first attempt was to form a rectangle tube by heating a piece of 40mm plastic pipe under the grill, and then forcing a piece of wood into the semi flexible plastic. It was easy to do, but I found an alternative. Later I found it easier to use discarded craft knife blade holders. These are ideal and will give adequate flow when the ends are removed. They are around 20mm wide by 12mm deep, so you will need to position the piece of tube (converted blade holder) in the centre of the shortened end glass and mark its position. The 30mm strip you cut off will now need cutting so that you have a piece to fit at either side of the rectangular tube.

 
How to convert the end glass, and the system in action.
The long grey pipe transfers water from the lowest tank to the highest, and was for trial purposes only. Later it was hidden at the rear, and could be a flexible type.

Silicone the two 30mm strips to the top edge of the shortened end, and onto the front or back glass as required. Do this by placing them edge to edge. You should now have a complete end, minus a gap in the middle which is 30mm wide. Cut two more strips of glass around 15mm wide and cover the joining of the 30mm strips and the shortened end glass. Do this by applying silicone to the strip, then position over the joins and apply slight pressure for a few moments. It will hold in place.

The only thing left to do is to now bond the rectangular tube into position. This is a bit messy, but I find the finger works best to spread the silicone around the rectangle tube. I let the tube overhang into the tank by around 30mm, and the rest extends from the tank side and will eventually overhang the next lower tank. The short overhang in the converted tank will allow me to add a piece of mesh over the opening if required to stop fry being passed from one tank to the next. Check to see it is well sealed, and don't be too worried about the top section being open, as the water will never reach that level.

Place the tanks in position and ensure that the one with the conversion is around 30mm higher than the other, and both are on a solid stand with a styrene base for each.

Any flexible tube around 12mm will do for the transfer water pipe, as all you really need is a pipe with an airline pushed in the bottom. I used a bit of garden hose for my trials, but you may want something better looking. The uplift pipe should always go in the lowest tank of all, as placing it elsewhere will cause one or more tanks to overflow. Adjust the air so that the water is lifted in the flexible pipe and flows into the upper of the tanks. The flow should only go into the upper most tank in the line of tanks, otherwise that tank will remain cold.

As the tank fills the water will begin to pour from the rectangular tube and into the next lower tank, then the next, then the next, until it reaches the lowest tank where it is forced back into the highest tank in the line. Even if you had ten in line, the effect would be the same, as each higher tank would overflow into the next lower one. All my tanks remained within one degree of each other, so I don't think it makes much difference which one the heater is in, but I suggest putting it in the tank that is the lowest one, the one with the uplift. The heater in the uplift tank is 150watt, but perhaps in winter this may need upgrading to a larger size.

Instead of an airlift you could of course use a powerhead. As long as the overflow rectangular tube is larger than the input of water coming into the tank, then the tanks will never overflow. A strainer mesh can be added to prevent fish moving tanks.

I would be pleased to hear any questions or opinions.  email:  pegasus-nz@paradise.net.nz

- Sid Smithies, also a New Zealander, uses the cascade system combined with filtration. For illustrations of his handiwork, see People/Sid Smithies