I came up with a better way to make a simple overflow for aquairuim tanks that are not predrilled. Take a 4" long section of 1" PVC pipe. Put a cap on one end. Drill 3/16 or largers holes, smaller than 3/16 will not work, completely around the 1" PVC Pipe, above the end of the cap. Put a 90 Degree on the other end of the PVC pipe. Drill a hole, just big enough to put an air tube through in the top of the 90. Push the air line through the hole into the 90. Take the cap off the other end, and put a aircore sand airstone diffuser (other bands may not work) on the end of the air line. Pull the air line down to where the bottom of the diffuser is even with, or as near as possible to even with, the bottom of the cap. Place the cap back on the 4 long section of 1'" PVC pipe. Adjust the air line upward a small amount if necessary. Do not go to far or the difuser will not work. Put a 2" piece of 1" PVC pipe on the open end of the 90. Place a another 90 on the the open end of the PVC pipe. This makes a 180 U from the tank to your drain line. Make sure to Glue this with PVC pipe glue. Attach the open end of the 90 to 1" line that leads to you drain line. You can connect to the drain line with a T if you are using  a 1" PVC drain line or you can use a converter (2" to 1") and a 2" tee, or just drop the end of your 1' line inside of the 2"or Larger tee, if you use a 2" or larger PVC drain line. I use a 2" PVC line on my system.  A note of caution; be sure to glue the 90's and their connecting 2" piece together tight. The 1' top of the line, that feeds to your drain line, where it connects to the 90 must also be glued. Make sure the hole for you air hose is tight and does not leak any air. Air leaks above the water line will cause this system to fail.
The two 90s and the cap cost about 50 cents each. A 5 to 10 foot section of 1" PVC costs about $2.50. A 1" tee costs about $1.00 and a 2" tee cost about $1.50. If you need it a 2 to 1 converter costs about 1.50. The whole thing using just 1" PVC Pipe costs about $5 and if you use a 2" drain the converter and tee makes it about $7. Plus you will have left over 1" PVC to use on additional tanks, reducing the cost per tank as much as $2.50. You can also purchase 90s and Ts in packs lowering your over all cost, if you are doing multiple tanks. These PVC parts are usually available at Lowes or Home Depo.
     This sure beats pre-drilling tanks, which can be very tricky, and the cost for an overflow box which runs about $60. It works on the same principle as an under-gravel filter. When the water level in the tank gets to low for the air to push it up through the 180, the overflow stops working. However, as soon as more water is added to the tank, the overflow will start working again. As long as you do not add water at a faster pace than the overflow can push out the old water, the tank should not overflow. Over time you will have to replace the defuser with new ones. Using this overflow in combination with a drip system and under-gravel filters powered by air, will dramatically reduce your tank maintenance time. 
     These air lifts use a large amount of air. It is best to have them on a line from a seperate air pump that your other tank air lines, spnge filters, or especially if you are using undergravel filters in deeper tanks. This sytems work well on glass or acrylic tanks; but, it will not work properly on plastic tubs. Anything shorter than 4" from the 90 to the cap tends not to work. Air lines with out a diffuser also fail. Some brands of difusers may not work or not work very well. More than 4" from the 90 to the cap may not work, especailly in smaller tanks. Even though the air line is about 4" below the top of your tank, the water level ususally does not drop more than 1 to 2" below the top of the tank using this system. 
     To save energy, you can shut off the extra pump to these lines when you are not adding water to your tanks. Another option is to use two values and a T to devert the extra air from the second pump into other air line when you are not using the lifts. If you do this, be sure not to close both of these values at the same time or you will blow apart your pump.

     For those of you that are not fimilar with a drip system, it is a system used to make water changes much easiler. Basically you drip fresh water into the system slowly and waste water is removed at the same or similar rate. The watse water can be removed through a direct line to a drain or sump. If you use a closed recyclying system, a drip, and an overflow can be added to the recycling sump, to acheive the same purpose. The big advantage to a direct in and direct out drip and drain system, however, is that a problem in one tank will stay confined to one tank. On the other hand recycling systems will spread the problem to all tanks. The two disadvantages to the direct in and out system are:  1) the PH can vary somewhat from tank to tank. However if you use the same amount of the same type cichlid or coral reef stones, or an equal mixture of these two type stones, the PH will be be similar in each tank. 2) Unless you can figure a way to add a UV Sterilaizer to the incoming water line, and be able to turn it off when the water is not flowing through it, you will have to depend on the quality of your incoming water. In most cases, especially if you have town or city water, this is not a problem.
     I use a Drip system along with sponge filters for my fish room aquairiums. This system was taught to me by Tony, of the former Tony's Tropical Fish in York, and improved upon by Lonny from the Lancaster Aquairum Club. Tony used it for over 30 years, in his stores. Tony used undergravel fiters rather than sponge filters. However, I have found that undergravel filters cause problems over time. Sponge filters or the old style box filter are a much better way to filter the water in this type system.  
     The way the drip system, that I use, works, is the incoming water runs through a whole house filter with carbon to remove the chlorine from the city water. A pressure reducer is used to lower the water pressure to a level that the PVC pipe, and values can handle. Water is mixed fom the hot and cold water pipes, and runs through an in-line themometer, so I can make the necessary adjustments to keep the water temperature at a safe level. When turned on the system pushes fresh water through the in-coming lines to values on each tank. Each value is set to a drip rate for the size of the tank. 
     With this system, I use a spomge filters in each tank powered by a large air pump. Since my incoming water is about 7.4 PH, the stones in my tanks are used to raise the PH to 7.8. Because the water drip is very slow, the PH remains in a safe range for most African Cichlids. The drip is run for 8 to 12 hours two times a week, and the need for stone cleaning is reduced to once a month, using this system. Sponge Filters usually need rinsed monthly as well. However, rinsing the sponge filters at the same time as a stone cleaning is not a good idea. Do so, can kill fish.
      One drawback to this system is high PH Cichlids, that require 8.2 and higher PH, can not tolerate my drip system's PH Range. For fish of this type, I need to set up temporary tanks that are not part of the Drip System, requiring buffing, and manual water changes. For this reason, I only offer high PH Cichlids on an special order basis.  

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