Convert to metric as needed, but here's instructions on how I make my dividers.
It's very simple.
1 length of 1/2" pvc
package of plastic tie wraps (10 or so) 5-6" length
2 1/2" pvc T's
2 1/2" pvc elbows
sheet of eggcrate (found in the lighting department at lowe's)
Measure the height of your tank from under the bottom rim to under the top rim.
Subtract 2"
Cut 2 pieces of pvc pipe that length
Measure the inside of your tank from front to back between the glass
Subtract 2"
Cut 1 piece of pvc pipe that length
Debur the ends of the pipe by scraping lightly on the inside and outside. I use a butter knife to do this.
put the two elbows on the piece you just cut
insert the other two pieces into the other holes on the 90
put the T's on the other ends
You should have a U-shaped frame now
Cut 4 4" pieces of pvc pipe, debur, and set aside for later
Insert the frame upside down in your tank to see if the fit is right. It should be snug, but don't force it. It's ok of there's a little gap, but not big enough for the fish to get through.
If it doesn't fit, try to seat the top pipe inside the elbows a little more. If that doesn't work, then remove one side and trim an 1/8" off of it. Debur, reseat, retest, etc.
Once you have the frame top fit, measure the inside of the frame from front to back. Put this measurement against the egg-crate. Find the nearest square and cut through (I use a butter knife again to break through) the size you need.
Use the tie wraps to secure the egg-crate to the frame. I start by putting two at the top then one on each side then work my way down.
Recheck the fit in the tank. Snug up the elbows if you need to. Once it fits, put it in the tank, then insert the 4" pieces into either side of the T. You'll have to clear the gravel at the bottom of the tank for it to fit.
Smooth out the gravel and you're done.
See this post for a pic of the divider in my tank.
http://www.aquariacentral.com/forums...d.php?t=176503