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Re: fertilizers - longish posting
At the beginning of April I set up a new 54 gallon planted tank with a sand
bottom. The lowest layer contains laterite as per instructions. At the
time, I was planning to not add any fish to this tank until and unless the
experiment either succeeded or not.
What I did was add Jobes flower spike bits deep into the sand (8:9:11),
along with Seachem Fluorish tabs and Aquarium Pharmaceutical Root tabs.
Since that time I have measured the phosphate levels in the water column and
they are close to zero. The only reason they are not at zero is that I was
forced to move some fish from another tank into this one. Hence there is a
little nitrate but not from anything added to the substrate, else the
phosphate levels would be a lot higher.
I've been following the levels of nitrate, phosphate etc. in this tank for 2
months now, and I have concluded that fertilizer pushed down into the sand,
at a 2 inch depth, does not enter the water column. I started with 48
vallisneria of 3 types, 3 Uruguay Swordplants and 20 Sagittaria subulata.
Now there are more Vallisneria than I can count, the swordplants are
developing beautifully and the sagittaria have also developed runners with
daughter plants, but not as profusely as the vals.
As a result of this experiment, I added bits of fertilizer spikes (about the
size of a very large pea) and Seachem Fluorish tabs into the gravel of my
planted 120 gallon tank. My previously (for over a year) languishing
cryptocoryne have taken off. They have grown into monster crypts within 5
weeks. This is an extremely heavily planted tank with CO2 injection. The
phosphate and nitrate levels are barely perceptible.
So, I question any advice wherein the addition of substrate fertilizer would
affect the water column adversely, resulting in algae. The 54 gallon tank
never developed an algae problem of any kind. It also has salvinia and
watersprite floating on top, but these were added only 4 weeks ago, by which
time I had already ascertained that the fertilizer added to the substrate
was not leaching out. These floating plants were added when the fish load
was increased dramatically by 3 blue gourami. The 120 gallon tank did not
have a significant algae problem when I added the fertilizer. The amount
and type has not increased. Both tanks receive PMDD at their weekly water
changes: 25+ACU- for the 120 gallon tank and 45+ACU- for the 54 gallon tank.
Furthermore, a few months ago I inquired on this list as to why new Anubias
leaves would be rotting off at the base of the stem. This was in a 65
gallon tank. I have not received a response to this. However, I have since
come to the conclusion that these plants do poorly if there is even a
moderately high nitrate level. I added duckweed and watersprite to the
surface in order to outcompete hair algae. As a coincidence, since that
time, no new leaves have rotted off either. The nitrate level in this tank
is also unmeasureable, whereas before, it could go as high as 25 mg/l. This
would make sense given that Anubias live, in nature, both emersed and
submersed. As emersed growths, they would be obtaining nitrogen from the
substrate only and the natural waters from which they originate and are
submersed in during the rainy season are low in nitrate also. BTW, the
leaves were rotting off both the Anubias which were tied to driftwood and
those that had their roots in the gravel but not their rhizomes.
My understanding, from contributors to this list, regarding substrate
fertilizers, is that they are added specifically to prevent algae growth by
not contributing fertilizer to the water column. Furthermore, it would
appear that there are plants, such as cryptocorynes, swordplants and
possibly even vals and sags that grow much better when substrate
fertilization is added.