[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
substrate pH and CO2 losses due to trickle filters
The optimum pH for nutrient availability is about 6.5 according to
terrestrial gardening reference books, aquatic botanists and experts
to whom I've spoken.
You can determine the pH of various substrate materials by mixing them
with water and measuring the pH of the water after a day or two. In
this way you can determine the relative acidic strength of various
types of peat and organic soils. You can do the same with soils
containing limestone but remember that dolomite lime or limestone is
very, very slow to dissolve and you won't reach equilibrium for a long
time. In the case of organic materials, these are also continuously
decomposing and releasing additional acids. You could probably measure
the pH accurately with a pH probe (although not the delicate ones)
Is there a standard method for measuring aquatic soil pH?
I've also read that aquatic soils over a long period of time tend to
naturally equilibrate at pH between 6 - 7; I suppose this process is
helped by the continuous input of fresh rain water and runoff.
If you had a very acidic peat and you decided to increase the pH by
the addition of dolomite (or other stronger lime), I'd be concerned
that the peat might begin to rot more quickly. Try to choose a type of
peat which is suitable for the environment you want to create. Acidic
environments are probably typical of tropical rain forest regions such
as SE Asia (Crypts) and the Amazon (Swords) where many of our popular
plant species are indigenous.
CO2 out-gassing with trickle filters:
Any surface disturbance will greatly affect the rate of CO2 transfer
to the atmosphere. If you have a 4 ft gas cylinder, I wouldn't be
overly concerned because you can simply dial up the injection rate to
compensate. Folks using yeast CO2 may need to be more concerned
because you have only a limited amount of CO2 available and the output
rates are not high compared to what you can get from a compressed gas
cylinder. In this case I've recommended not using the sump trickle
filter method; properly sealing the sump to create a high CO2
environment in it is also going to create an environment without O2
since oxygen cannot diffuse into the chamber without CO2 diffusing out
just as fast. The lack of oxygen probably defeats the purpose of the
filter (nitrification) unless you only use it for mechanical
filtration but I suppose the oxygen can come from the aquarium
water... I think George advocates sealing up the sump chamber [he'll
probably correct me ;-) ] If George says you can do it, you can
believe it but make sure you get that advice from the horse's mouth.
[sorry George, no pun intended ;-) ]
Another trick I've used with the cheap box filters you hang on the
side is to silicone a thin sheet of plastic to the outflow to reduce
Experiments by George indicated a rapid increase in CO2 out-gassing
with even minor disturbance of the water surface such as created by
the outlet of a submerged powerhead aimed parallel to the surface. I
try to aim my powerhead at a downward angle but not so that it
disturbs the substrate either. After a week or so, my powerhead inlets
tend to get partially clogged up and the reduced current is not a
problem. You can also adjust the flow rate on many models.
Steve P in Vancouver where April showers have brought the flowers!