I am testing out a new meter with a bunch of water quality probes in my fish tanks. I have probes to measure pH, conductivity, temperature, and dissolved oxygen as well as ion selective probes for calcium, chloride, ammonia, and nitrate. I have had variable success is acquiring reasonable data with the ion selective probes, of which the nitrate probe seems to have the most functionality.
Anyway... I do frequent small water changes on my trout tank, 5 gallons at a time, with RO water. I do this usually once or twice a day. I have been mostly collecting instantaneous readings of water parameters every few days for a while now. Last night, I decided to record time series data as I did a couple of water changes. Can only run 3 probes at a time, and the ion probes only measure consistently in a still sample (in a beaker, for example) so I have gone with the three that should have the most meaningful data through a WC.
The top graph is temperature, and the orange lines indicate the initiation of RO water addition. In the first water change, you can see the individual temperature spikes, as I added each of the 4x 1.25 gallon containers. The temperature probe was very close where I added the new water (new water was 22*C). The chiller kicked on just after 20 minutes of data collection, and you can see the downward trend in the temperature before the second water change.
The second graph is conductivity, and that probe was on the complete opposite side of the tank from where I added the RO water (~5 microS/cm) so there is a slight lag in the graph, but it makes sense overall.
The third graph is pH, and this is where I am less clear... The pH probe seems to be slightly effected by current, and if you stir the probe, the pH rises slightly. The pH of the RO water going is was ~ 6.5, so I would expect a slight drop in pH as the RO is added to the tank. The initial spikes on the first change are likely from the added current from pouring the water (probe was next to the temp probe, same side of tank that water was added). One those stabilize, there is a brief time of slightly lower pH, then it hits about the same stable point as before. What really has me puzzled is the increase in pH starting around 16-18 minutes, while nothing is going on. The graph makes it look drastic, but it is only about 0.1 shift.
I figure that this thread will draw some views, but I sort of expect radio silence on replies, but if you have any thoughts, I am ready for them... I am going to go do another WC in a minute, and I will set the probes up again...
Anyway... I do frequent small water changes on my trout tank, 5 gallons at a time, with RO water. I do this usually once or twice a day. I have been mostly collecting instantaneous readings of water parameters every few days for a while now. Last night, I decided to record time series data as I did a couple of water changes. Can only run 3 probes at a time, and the ion probes only measure consistently in a still sample (in a beaker, for example) so I have gone with the three that should have the most meaningful data through a WC.
The top graph is temperature, and the orange lines indicate the initiation of RO water addition. In the first water change, you can see the individual temperature spikes, as I added each of the 4x 1.25 gallon containers. The temperature probe was very close where I added the new water (new water was 22*C). The chiller kicked on just after 20 minutes of data collection, and you can see the downward trend in the temperature before the second water change.
The second graph is conductivity, and that probe was on the complete opposite side of the tank from where I added the RO water (~5 microS/cm) so there is a slight lag in the graph, but it makes sense overall.
The third graph is pH, and this is where I am less clear... The pH probe seems to be slightly effected by current, and if you stir the probe, the pH rises slightly. The pH of the RO water going is was ~ 6.5, so I would expect a slight drop in pH as the RO is added to the tank. The initial spikes on the first change are likely from the added current from pouring the water (probe was next to the temp probe, same side of tank that water was added). One those stabilize, there is a brief time of slightly lower pH, then it hits about the same stable point as before. What really has me puzzled is the increase in pH starting around 16-18 minutes, while nothing is going on. The graph makes it look drastic, but it is only about 0.1 shift.
I figure that this thread will draw some views, but I sort of expect radio silence on replies, but if you have any thoughts, I am ready for them... I am going to go do another WC in a minute, and I will set the probes up again...
