External filters extract water from the tank via a pipe and return it via another. How these pipes are augmented is a complicated, and extremely controversial matter.
A spray bar is an augmentation of the return pipe where the water is squirted out of a number of holes in a rigid plastic pipe.
>>> How affecttive is the spray bar and what does it even do???
2 Questions so...
>>> How affecttive is the spray bar
It returns all of the water to the tank, it is thus, 100% efficient, (barring leaks).
>>> what does it even do???
Hmm, now we run into controversey. It depends on where you place it, and at what orientation, what you want to do with the tank and who you ask! It can be placed...
a) Above the water surface angled down
b) Above the water surface angled horizontally, (or at an angle)
c) Just below the water surface angled along the glass up
d) Just below the water surface angled horizontally
e) Just below the surface angled down
f) Just below the surface angled along the glass down
g) Well below the surface angled up
h) Well below the surface angled down
i) Well below the surface along the glass downwards
j) Vertically into the tank
k) Vertically along the glass
l) Vertically against the glass
... and there are various perverse variations such as at an 45degree angle with 2 hole above the water surface. You think I'm kidding? I've seen lengthy debates on this topic and there are advocates of each of these, and other strategies that will write a full monograph on their take as to why their method is better.
There are a few things you need to decide when it comes to spray bars. Are you fish based, and don't really care about plants? Do you want to do well with live plants? Is your tank sensibly stocked? What are your personal æsthetics?
A few general rules.
Fish need Oxygen to survive. O2 gets into thew water at the surface. The more surface movement you have, the more O2 will dissolve.
O2 will diffuse throughout a tank given enough time. O2 will be available to all the fish if there is a good circulation in the tank.
Plants need CO2 to grow. CO2 is difficult to dissolve and comes out of solution easily, to keep CO2 in your tank water, you want low surface movement.
Some fish like high energy environments with a current, others are still water fish and are stressed by flow and the effects of bubbles.
Some people like to see bubbles.
Some people like to see their plants waving about.
In some situations, the room noise created by an above surface spray bar is unacceptable.
YOU now need to decide if a spray bar is for you, and if so, where YOU will place it!
If you want to maximise surface movement, choose d, or b. (d better).
If you want the maximum circulation for O2 distribution, choose h or e.
If you are a plant enthusiast and need to hold CO2, choose i.
For maximum in tank current, choose e or j.
For maximum bubbles, choose a.
For minimum noise choose anything but a or b.
I have more to say, but I hav to go out now. I'll edit this later!
