To build the HOB:
I used a 10inch household water filter casing, a 10 inch piece of 20mm PVC (Ignore the white elbows as they were for something else)
A 20mm ball tap with a 19mm elbow on one side (Not in picture) and a 19mm "Y" splitter on the other side.
Take the 20mm PVC and drill as shown (Bigger holes at the bottom, getting smaller towards the top):
Open the filter casing and get the lid:
Attach the drilled 20mm PCV as below:
Take some filter media (This is a 20 micron standard household cartridge, but you can use whatever you like)
Place it over the 20mm PVC:
Then screw the filter case back together.....
Now for the plumbing:
Get your power head and a 19mm elbow and attach it to the powerhead with 18mm hose,
make sure the long length will reach up out of the tank,
at the top connect another 19mm elbow then connect that to one end of the Y splitter on the ball tap
on the other side of the Y splitter, I connected a short length of pipe, with some standard garden hose attachments that had another tap which is turned off off (the orange tap), ill explain more about this later.
next connect the 19mm elbow from the other side of the ball tap to the "IN" side of the filter, then connect the out to something that will drain the water back into the tank....and your done!!
![20150429_144255.jpg 20150429_144255.jpg](https://www.monsterfishkeepers.com/forums/data/attachments/862/862391-a725a0a9329eb9d32949ffd54b11110a.jpg)
(I swapped the housing on my filter to clear so i could see what was going on)
NOTE: regarding the Orange tap and the ball tap, when the orange tap is off and the ball tap is on the water flows through the filter, if i turn the ball tap off and the orange tap on, it acts as a water changer, I just attach some garden hose to the orange tap and put the hose out the window and i have a 2000L/h water change!!
This is a pic of another unit i have made thats attached to the outlet of my canister filter, this one has a dual chamber, the first (the one at the back) has a 20 Micron filter, the second contains 1L Macropore, then it goes to a 40w UV
My canister is an Eheim 2264, so i direct about 85% of the output to the spraybar, the remaining 15% goes through this dual chamber, as UV and Macropore with best with slow flow, they are getting about 800L/h
Hope that helps....
![20150429_145947.jpg 20150429_145947.jpg](https://www.monsterfishkeepers.com/forums/data/attachments/862/862394-8220d1152186a9a90cfda02f352c1c51.jpg)