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I have often wondered how much material (is it all detritus?) is removed from a substrate when it is vacuumed. I am moving the contents of a 40 gallon aquarium to a 75 gallon aquarium and some or all of the sand is going. I am taking the opportunity for a small substrate study and I am looking for any comments or ideas on the approach.
The system is a four year old fish only aquarium with 1-2 inches of fine silica sand when spread evenly, but now there are some sand dunes 2-3 inches deep and some bare spots. In today’s substrate survey, I vacuumed up sand along with tank water. I let the sand settle and poured off the water. The sand slurry was poured into a graduated cylinder and allowed to settle. The volume of sand was 77 mL, representing a roughly 2 by 2 by 1 inch deep volume of substrate. The water was centrifuged, leaving a very dark pellet of sludge, about 1.3 mL in volume. Under the microscope, the sludge consisted mostly of amorphous and translucent looking material with only a scattering of recognizable forms.
On a volume basis, the sludge makes up around 2% of the substrate volume. I have no reference to say whether this is good, bad or a so-what. I do wonder if the above approach might be a way to characterize the condition of a substrate. A new substrate might have no sludge, a one year old substrate a little, a vacuumed substrate might have another level. Does the amount of sludge level off after some time? Can sludge accumulate indefinitely or is there a physical limit? Does the amount of sludge reach a steady state in a healthy system?
Dan
The system is a four year old fish only aquarium with 1-2 inches of fine silica sand when spread evenly, but now there are some sand dunes 2-3 inches deep and some bare spots. In today’s substrate survey, I vacuumed up sand along with tank water. I let the sand settle and poured off the water. The sand slurry was poured into a graduated cylinder and allowed to settle. The volume of sand was 77 mL, representing a roughly 2 by 2 by 1 inch deep volume of substrate. The water was centrifuged, leaving a very dark pellet of sludge, about 1.3 mL in volume. Under the microscope, the sludge consisted mostly of amorphous and translucent looking material with only a scattering of recognizable forms.
On a volume basis, the sludge makes up around 2% of the substrate volume. I have no reference to say whether this is good, bad or a so-what. I do wonder if the above approach might be a way to characterize the condition of a substrate. A new substrate might have no sludge, a one year old substrate a little, a vacuumed substrate might have another level. Does the amount of sludge level off after some time? Can sludge accumulate indefinitely or is there a physical limit? Does the amount of sludge reach a steady state in a healthy system?
Dan