"Sean Dinh" wrote in message
...
They are superior in term of ammonia and nitrite removal. There is still
nitrate left.
George wrote:

Hmmm. If the filter is so superior, why do they have pea green soup for
water?
I only had this problem once, immediately after I set up my pond three years
ago. I haven't had it since.

I might experiment with a possible nitrate solution this year. If you're a
marine aquarium buff, and I am, then you know that everyone is moving completely
away from artificial filtration and moving to natural filters. What this means
is getting rid of all the foam, bioballs, and most any other filter media that
convert ammonia and nitrites to nitrates. What is substituted for these are a
refugium (garden pond people are already doing this with veggie filters), live
rock, and thick sea sand on the bottom with a current flowing over it. The idea
of using the sand substrate for filtration (without using the terrible
undergravel filters that suck up all the gunk in the tank and then let it
decompose on the bottom, adding to the nitrate problem) is that sea sand acts as
a nitrate filter, because the water flow through it is very slow compared to
other filters. With a current flowing over top of the sand (as you wold have in
a natural stream), a slow current is induced in the sand. So it allows for the
growth bacteria that will utilize the nitrates. These bacteria also grow in the
live rock. I know that everyone is against placing rock or any substrate in the
bottom of their ponds for various reasons. What I plan to do is to change the
setup on my main filter by pulling it completely out of the pond (the filter
material is all from porous rock). This will allow more room for the fish to
move around in. It will also allow me to build a fresh water reef on top of an
8 inch coarse, dark sand base. The final modification will be to divert some of
the outflow from the primary filter to allow it to flow slowly over the sand
base and more strongly across the reef structure (this might involve getting a
bigger pump, or a second pump). It works very well for sal****er tanks, so I'm
strongly considering trying this method.