Please note: This is the version that was posted online in early 2012. While the majority of the information presented here is still correct, there are a few things that are outdated. I've been meaning to update this for quite a long time, if you have any questions, you can click the Discussion tab and ask!
Preventing water creep along the pipe
This is an important part of the slot pipe design. The issue here is that when you are running water though a horizontal pipe with a slot in the bottom of it, the water has a tendency to creep along the bottom edge of the pipe, not matter how perfectly horizontal you install it. If your Algae Scrubber is positioned completely over your sump, this may not be a big issue, as any errant flow will just drip into the sump. If your pipe ends extend close to the edge of the sump however, a steady trickle of water can result in gallons of water on the floor. I can attest to this.
The solution is very simple. Right at the point where the slot ends, place a large plumbing gasket, such as an o-ring (use several, they’re cheap), or even a bulkhead gasket. The point is that it needs to prevent water from getting past it. I can tell you from experience that a standard zip-tie will not work – the profile is too low.
In many cases, you need to put this piece on the pipe before you weld the cap on the end of the pipe, or else it will be very difficult to install. This one is a ballcock washer, and definitely needs to be installed before the cap is installed:
Here’s what I used on the latest mod to the Algae Scrubber I run
I found these at Ace hardware in the plumbing gasket section. I forgot to put them on before solvent bonding the ends on, but luckily they were flexible enough to get over the end cap. They work fantastic!
As far as spray and salt creep is concerned, you want to avoid buildup on the lamp itself. No matter what you do, there will still likely be some buildup due to evaporation, so you will want to wipe off the lamp or fixture periodically (as needed). Make sure the lamp has cooled down, remove the lamp if possible, and wipe it down with a soft cloth and warm water. This is rather easy to do in place with T5HO lamps, and more difficult for spiral and multi-tube CFLs; just be gentle so you don’t crack the tube.
The water will cascade down the screen smoothly, and then drop off the bottom edge. If you don’t let the bottom of the screen sit in the water, it’s going to pour off and crash down, and splash everywhere. That’s not the problem I’m discussing here, I’m talking about spray from the slot pipe or screen.
The ideal solution is to block the source of salt creep or spray – the slot pipe itself. While 99.99% of the water that cascades down the screen will stay on the screen, occasionally there will be droplets of water that pop and fly around, and over time these can cause salt creep.
The most recent and effective solution to the spray issue is also one of the cheapest and simplest. Saran Wrap!! I don’t have a picture of this, so just use your imagination: take a piece that is a little longer than the slot and wide enough to wrap around the pipe plus about an inch or so, drape it over the pipe, and touch it to either side of the screen. Water tension does the rest, and the Saran Wrap suctions onto the screen. Presto. No spray (from the slot). You still might get some droplets randomly flying off the algae mat, so other protection might be necessary, but the slot spray is definitely the biggest culprit, and Saran Wrap is a great weapon.
Aside from Saran Wrap, the best spray blocker is a box that totally encloses the screen on all 4 sides and bottom, and has a removable lid. Such a box would have a drain hole in the bottom, and would typically be made out of acrylic, but could be made from glass also. This is beneficial for other reasons too, but we’re just talking spray blocking right now.
Closing the top with a lid, or at least extending the blocker up to the top of the slot pipe, will minimize the random drops that occasionally fly upward, as well as evaporation. A lid should not lip over the outside of the box, rather the inside so that any condensation will tend to stay inside the box.
The next best would be an enclosure with an open bottom. The advantage to an open-bottom enclosure is that it's easy to build. If you extend the screen to the water level inside the sump, you can nearly eliminate noise and microbubbles. Pictures illustrate this best:
The most basic full-screen spray blocker would just be a couple of plastic panels draped over the tube. Here are a few examples:
I don’t recommend enclosing CFLs in glass or plastic jars. IMO, it is difficult to allow for adequate air convection with such an arrangement. CFLs get hot even with air convection, and if a hot lamp gets in contact with the plastic, it could melt and might start a fire.