Be warned, it's loooooooong:
--I am participating in an upper-level college biology class in which we are conducting our own experiments in small groups. My group's goal is to determine whether a Domino Damsel (Dascyllus trimaculatus) could actually inhabit an aquarium without salt. Salt is the ONLY variable we're changing (aside from dextrose, more on that further down), meaning the temperature, pH, waste levels, water level, and so on are all being kept at constant levels as they are found in it's natural habitat.
More details for those of you still reading--We are quite aware of the variance in osomoregulation needs in a hyper- vs hypoosmotic environment. We are using a 10gal glass aquarium, HOB filter, powerhead/filter hybrid for extra water current, heater (78 deg F), hood w/compact flourescent lights, naturally-colored aquarium gravel (neutral, does not affect pH or leech toxins in fresh or salt water), "Instant Ocean" aquarium salt, and marine buffer (pH 8.2).
As a sort of control, two mollies--commonly known as brackish water fish--are also in the tank with the single domino damsel (I know, a larger test pool would give more accurate results, but everybody knows how limited school funding has become, much of the equipment was donated or purchased with our own money). The tank features a permeable mesh divider to separate the domino from the mollies and prevent excessive aggression while allowing the water to move freely between the two zones.
Our procedure thus far, has involved small, incremental dilution of the salt in the tank by removing water from it and replacing it with fresh water (pH 8.2, 78 deg. F, purified via reverse osmosis and deionization). While we would like to take it slower, we do have project deadlines to meet, so we lower the specific gravity by an average of 0.002 each week (ex: after a few weeks of acclimation before making salinity changes, the first water change brought the S.G. from 1.020 to 1.018)
One article in a fish magazine from 1968 (which our instructor just happened to have lying around) had a brief few paragraphs reporting on a japanese man who successfully kept a number of marine fish (and a few inverts.) with freshwater fish with no salt whatsoever for a long period of time. From this very short article, we were able to see that he used grape sugar (dextrose) to supposedly ease the stress of the transition. Therefore, we have added 1cc dextrose in 5% saline solution (per 10 US gal of aquarium water) on the first day we lowered the salinity, .5cc on week 2, and a final .5cc on week 5.
At this time, the specific gravity is 1.006, and all three fish are thriving as far as we can observe externally. When I say that, I mean that even the damselfish is still darting about as though it were back on the reef, displaying toward the mollies in a show of force on occasion, showing perfect coloration, and feeding readily (even the algae on the back of the tank is still alive).
We have had a heck of a time finding any particularly reliable source of information (recent peer-reviewed journals and the like) that deals more directly with the topic. This post is a bit out of frustration and desperation!
What I would like to know from you is:
1. if similar experiments have been done under relatively controlled conditions or with some explaination; if so, please elaborate or provide links!
2. Do you think it's possible? Please elaborate, try to convince us
3. What are some changes you would suggest? If you have any advice, comments, or questions, we'd love to hear from you.
Thank you so much for your time,
the dude with the Sweet Fishbox
--I am participating in an upper-level college biology class in which we are conducting our own experiments in small groups. My group's goal is to determine whether a Domino Damsel (Dascyllus trimaculatus) could actually inhabit an aquarium without salt. Salt is the ONLY variable we're changing (aside from dextrose, more on that further down), meaning the temperature, pH, waste levels, water level, and so on are all being kept at constant levels as they are found in it's natural habitat.
More details for those of you still reading--We are quite aware of the variance in osomoregulation needs in a hyper- vs hypoosmotic environment. We are using a 10gal glass aquarium, HOB filter, powerhead/filter hybrid for extra water current, heater (78 deg F), hood w/compact flourescent lights, naturally-colored aquarium gravel (neutral, does not affect pH or leech toxins in fresh or salt water), "Instant Ocean" aquarium salt, and marine buffer (pH 8.2).
As a sort of control, two mollies--commonly known as brackish water fish--are also in the tank with the single domino damsel (I know, a larger test pool would give more accurate results, but everybody knows how limited school funding has become, much of the equipment was donated or purchased with our own money). The tank features a permeable mesh divider to separate the domino from the mollies and prevent excessive aggression while allowing the water to move freely between the two zones.
Our procedure thus far, has involved small, incremental dilution of the salt in the tank by removing water from it and replacing it with fresh water (pH 8.2, 78 deg. F, purified via reverse osmosis and deionization). While we would like to take it slower, we do have project deadlines to meet, so we lower the specific gravity by an average of 0.002 each week (ex: after a few weeks of acclimation before making salinity changes, the first water change brought the S.G. from 1.020 to 1.018)
One article in a fish magazine from 1968 (which our instructor just happened to have lying around) had a brief few paragraphs reporting on a japanese man who successfully kept a number of marine fish (and a few inverts.) with freshwater fish with no salt whatsoever for a long period of time. From this very short article, we were able to see that he used grape sugar (dextrose) to supposedly ease the stress of the transition. Therefore, we have added 1cc dextrose in 5% saline solution (per 10 US gal of aquarium water) on the first day we lowered the salinity, .5cc on week 2, and a final .5cc on week 5.
At this time, the specific gravity is 1.006, and all three fish are thriving as far as we can observe externally. When I say that, I mean that even the damselfish is still darting about as though it were back on the reef, displaying toward the mollies in a show of force on occasion, showing perfect coloration, and feeding readily (even the algae on the back of the tank is still alive).
We have had a heck of a time finding any particularly reliable source of information (recent peer-reviewed journals and the like) that deals more directly with the topic. This post is a bit out of frustration and desperation!
What I would like to know from you is:
1. if similar experiments have been done under relatively controlled conditions or with some explaination; if so, please elaborate or provide links!
2. Do you think it's possible? Please elaborate, try to convince us
3. What are some changes you would suggest? If you have any advice, comments, or questions, we'd love to hear from you.
Thank you so much for your time,
the dude with the Sweet Fishbox
My understanding is that OSU is great for those focused more on intertidal study, and the University of Oregon is more geared towards deep-sea research. There seems to be a similar situation between two schools in Hawaii too--> don't take my word for it though, I haven't actually gone to all these schools
He has a good point.