Saltwater Aquariums
*******If you have a problem with one of the tanks please refer to the Tank Troubleshooting page.********
We have ten 75-gallon aquariums that house the crabs and lobsters used in electrophysiology experiments within the Marder Lab. Below is some information on how these tanks work and their daily maintenance requirements.
How the tanks maintain their water depth
The tanks have two water reservoirs, the main reservoir/chamber (where the animals go) and the overflow chamber. The water depth can be different in the two reservoirs with the water in the main chamber being deeper than in the overflow reservoir. There are slots in the wall between the two reservoirs and when the water in the main reservoir is above them water flows into the overflow area. After the overflow area, each tank has a filter system. The outflow pipe between the overflow chamber and the bottom reservoir causes a constant flow of water from the main chamber into the protein skimmer reservoir. Before entering the protein skimmer reservoir the water flows through a filter chamber where large debris is removed from the water onto a filter. The water then passes through spiky biotic filter balls, which add calcium and maintain the tank's bacterial colonies, before passing into the protein skimmer reservoir via a sponge to remove any other debris that hasn't yet been removed from the water.
There are 2 pumps in the protein skimmer reservoir. One is integrated into the protein skimmer and pumps water into it. Air is added to the water to make it froth (the amount of air added can be adjusted as needed via a vertical control pipe on the skimmer). As a result of the frothiness, any protein in the water gets pushed to the top and into a container for daily removal, when adjusted to the correct height. The other pump keeps up a constant rate of water flow from the protein skimmer reservoir through the chiller and then back to the main tank reservoir.
The flow rate from the main reservoir to the filter chamber and protein skimmer reservoir depends on how deep the water is in the main reservoir. If the water is above the overflow slots then the water will flow from the main to the filter chamber. Thus for a given pump rate, the water in the main reservoir will naturally come to a depth such that the flow rate out of the main chamber equals the fixed flow rate into the main chamber from the chiller. This is a stable equilibrium: If the water in the main reservoir gets deeper, there will be a net flow out of the main reservoir, until it comes to the equilibrium level. If the water in the main reservoir gets shallower, there will be a net flow into the main reservoir, until it comes to the equilibrium level. Thus by setting the pump rate, you are effectively setting the equilibrium water depth in the main chamber.
One consequence of all this is that the equilibrium water depth in the protein skimmer reservoir is determined by how much water is left over in the tank after the main chamber comes to its equilibrium depth. So if you try to increase the water depth in the main chamber beyond this by adding water to it, the tank will eventually (typically after about 15 min) come to an equilibrium where the water in the main tank is the same as before, and the water in the protein skimmer reservoir is higher as if you had added that water directly to the skimmer reservoir. Similarly, if you take water out of the main chamber, the tank will eventually equilibrate to a state where there's the same amount of water in the main chamber, and the protein skimmer reservoir is lower as if you had taken that water directly out of this reservoir initially. In contrast, if you add/subtract water from the skimmer reservoir, the level of water in the skimmer reservoir will happily stay where it is just after you add/subtract the water, and the water level in the main tank will not change.
Another consequence of all this is that any water lost to evaporation (from either chamber) ends up lowering only the water in the filter chamber. Yet another consequence is that you can judge how much water the pump is moving by looking at the rate water is flowing through the filter chamber. For a tank at equilibrium (i.e. if no water has been added or subtracted recently, and you haven't fiddled with the pump recently), these two rates are equal. So if the water is just dribbling into the filter chamber, that means the pump is not pumping a lot of water.
Daily Saltwater Tank Checking Procedure
All alterations of temperature, salinity, water levels, and the number of dead crabs (if there are any) should be recorded on the tank log, along with the date, time, and initials of the checker. The tank log is on the front of each tank. Make sure to check the tank log before making any changes to the tanks in case someone else has already made the desired changes but they have not had time to take effect. It is the responsibility of all lab members who use the tanks to check the tanks and remove dead crabs immediately. The lab technicians are responsible for the overall maintenance of the tanks which includes frequent checking of tanks, full cleaning of tanks when necessary, and ordering tank room supplies.
***A Daily Tank Maintenace sheet should be filled out with each tank's temperature, salinity, pH, and the number of crabs in the tank before the daily tank cleaning is done.***
Temperature: On each tank is located a thermometer to monitor the tank's temperature. The temperature should read between 10-12C, for general-purpose crab tanks. If the thermometer is reading a high temperature first check that it is in "water" and not "air" mode (there is a little switch on the left-hand side of the thermometer). If that doesn't resolve the issue, use a thermometer that you know is working to verify the water temperature is actually too high and there isn't some other problem with the thermometer (a few backup thermometers are always kept on hand in case one breaks–if you open the last one be sure to let the lab manager know so more can be ordered). The temperature acclimation tanks should be at the temperature specified on the label on the front of the tank. If the temperature is off, adjust the set temperature on the control box located at the front of the tank near the compressor.
Salinity: Place the hydrometer (which can be found next to where the Daily Tank Logs are kept) into the tank. The hydrometer will float at the surface of the water, and the level at which it floats indicates salinity. It should be floating with the water level within the range of the green band. If it’s floating too high (the green band is totally out of the water) the salinity is too high. If it's floating too low (the green band is totally submerged) the salinity is too low. *
*Once the daily log is complete, use a siphon to vacuum any debris out of the tanks and to exchange at least one 5-gallon bucket of water from the tank. If the salinity was too high exchange this water from the tank for the same volume of fresh, salt-free deionized water. If the salinity was too low, then extra salty saline needs to be added to the tanks. If the salinity is low by only a little bit, or if it is normal, the saline to be added does not have to be extra salty, it can be just the right amount: dissolve 1 cup of salt in a bucket of water. In either case, the new salt should be totally dissolved in the saline bucket before being added to the tank. Pour any new water, fresh or otherwise, into the front reservoir where the protein skimmer is located, as this will prevent the crabs from experiencing shock due to new unacclimated water. Both the temperature and salinity should be checked daily.
Lobsters and Crabs: The animals in each tank should be checked to see if they are alive. One can tell if they are alive by checking to see whether they are flicking their antennae. If they are, the crab/lobster is alive. If they aren’t, they could still be alive and should respond to being pushed around. Lobsters that don’t are dead, so are most crabs. For crabs, if they don’t respond, one can confirm the death by picking the crab up from its back leg and bringing it out of the water. If it pulls its claws and legs in, it’s alive. If the claws and legs are limp and droop down, the crab is dead. Sometimes it can be hard to tell, and a definite confirmation is given by the slightly inappropriate test of opening the tailpiece that covers the animal’s sexual organs. Live crabs get very angry, as they should, dead ones don’t. Any dead animals should be disposed of in the carcass freezer in the tank room. This carcass freezer is reserved for undissected, deceased crabs and lobsters.
Water Levels: The water level in the front compartment of the tanks should never be allowed to drop below the level of the top of the outflow of the skimmer's pump; it could burn out. That would be very bad. If the water level is low, add saltwater to the front compartment up to the indicated max fill line, depending on the salinity of the tank. It is better to keep the water level below the indicated line, but have the pump submerged, as this will facilitate the protein skimmer working more efficiently.
Full Tank Cleaning Procedure
Approximately once a month tanks need to be cleaned more thoroughly than the daily maintenance allows in order to remove algae and unwanted bacteria that have accumulated in the tank. This cleaning allows for a tank to reset to baseline healthy levels.
Remove all animals from the tanks being cleaned and don’t put them back for 24 hours. Up to 8 crabs per tank and up to 4 (2 if possible) lobsters per tank during this time. Animals cannot go into cleaned tanks until the following day when the tank has cycled overnight.
Turn off the tank via the power switch.
Scrub the sides of the tank, the bottom of the tank, the back part of the tank behind the Y tube, the parts in and around the protein skimmer in the bottom reservoir, any surface where algae may grow using the various brushes--NO SOAP!
Use warm water to clean the protein skimmers (the lid, removable reservoir, and large main skimmer parts). In cases where the large part is really dense with algae, use the DI water spigot to “power wash” them down. Again, no soap, as goes for everything.
Remove the filter in the drawer and replace it. Blue side up.
Remove the sponge filter at the back of the reservoir on the bottom and rinse clean with hot water. These are the rectangular black or green sponges. Put back when clean.
Use a siphon to vacuum out the debris that settles in the tank and bottom reservoir.
Remove ~⅓-½ of the tank’s water volume (2 full buckets)
Add new saltwater to the tank and turn the tank back on.
Sponge the top of the tank with warm water only to remove excess salt. Remove lids and rinse them in the sink with warm water.
Add 1 cap of algaefix and 1 cap stability to the tank.
Clean sink and jugs as usual.
Mop the floor to clean up excess salt and water.
No animals in the cleaned tanks for 24 hours. Before adding animals back the next day, check to see that everything is normal, ie. temperature, etc.
*all other tanks not full cleaned that day still have to undergo a daily tank clean