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Update on plenum tank
Some interesting observations. It's a 60 gallon 36x18x24 with a reef style
plenum made with 3 inches of 2mm gravel with laterite in the lower third, PMDD
fertilization regime, 175 watt 10K MH lamp. Filter is a HOT Magnum with peat
and ceramic noodles. Set up now for about 3 months. To get the plants really
going I have to add big doses of PMDD, so the plenum may actually be a drag on
nutrient availability. Large bubbles erupt from the substrate on a regular
basis (nitrogen gas?) and I have to add about eight times the recommended dose
of KNO3 to keep nitrates in the 3-5 ppm range, so the plenum seems to be doing
its thing in terms of denitrification. I took that as a "go" to add more
fish, so I did. The plants pearl, and when touched by the fish, a cloud of
tiny bubbles are knocked loose. Brush algae became a problem prior to the
current lighting but is slowly receding. Yesterday I added several clay balls
made from sandy loam and vermiculite hoping to slow the water flow through the
substrate a little and to give shallow roots something to hold onto. Being in
Texas where its been over 100 for a month, and being a built-in tank against
an exterior wall, the tank is hovering near 88 all the time. If I were using
substrate heating, it would never come on, so from that standpoint the plenum
has an advantage. Still too soon to tell if it's gonna work in the long run.
Tom