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*******If you have a problem with one of the tanks please refer to the Tank Troubleshooting page.********

In Volen 017A we have ten 75-gallon aquariums that house the crabs that are 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 the 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 pump pumps water into the protein skimmer. Here is where air is added to the water to make it froth (the amount of air added can be adjusted as needed via a stopcock on the airline). 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 basically 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 basically 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 eventuate 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 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 to 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 the top/front of each tank is located a thermometer to monitor the tank's temperature. The temperature should read between 10-12oC, 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 that there isn't some other problem with the thermometer (a few back up 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 their label in 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 Thermometer/Hydrometer (T/H–can be found on the cart where the Daily Tank Logs are kept) into the tank. The T/H 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 on the T/H. If it’s floating too high, as in the green band is totally out of the water, the salinity is too high. If the T/H is floating too low, as in the green band is totally submerged, the salinity is too low for the same volume of extra salty deionized water. *

*Once the daily log is complete, use a siphon to vacuum any debris out of the tanks and to exchange 1-2 5 gallon buckets 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 pump; it could burn out. That would be very bad. If the water level is low, add deionized water or salt water 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.

  1. Take any animals and put them in another tank.
  2. Turn off the tank via the switch on its respective outlet.

  3. Scrub the sides of the tank, the bottom of the tank, the parts in and around the protein skimmer in the bottom reservoir, any surface where algae may grow using the available brushes. It may help to remove a few buckets of water first.

  4. Remove the filter from the filter drawer and replace if needed.

  5. Remove sponge filter at the back of the protein skimmer reservoir and rinse clean. The sponge should appear blue and not brown.

  6. Replace both filters.

  7. Use a siphon to vacuum out the debris that settles in the tank and bottom reservoir. Leave a few buckets of the old water in the tank to allow for healthy bacterial colonies to grow.

  8. Add new saline to the tank.

  9. Plug tank back in and turn it on.

  10. Use wypalls with warm water to wipe salt from the outside of the tank and its lid.
  11. Allow the water level to equilibrate and add more saline as needed.
  12. The temperature will take longer, check that the next day.
  13. Allow a few days for the tank to acclimate to normal levels before placing animals in the tank.

Ordering Animals

Crabs and Lobsters are ordered by the lab manager when supplies are low. The lab manager must be notified if animals have been ordered someone else so that repeat orders are prevented. Phone numbers are posted next to each communal phone in the lab (including in the tank room).

  1. Call Absolute Delivery and state you are from Brandeis and have a package for pick up at "Commerical Lobster". Make sure to get a rush delivery to ensure the minimal amount of time exposed to the air for the animals. Also, ask the courier when they think they'll be picking up the package from "Commercial Lobster" so you can give the suppliers an estimated time of arrival. Their number is 781-792-1100. They will ask how many boxes are to be delivered, usually, it is only one box.
  2. Call “Commercial Lobster” and ask for X number of crabs or lobsters for the Marder Lab at Brandeis University. We usually order about 20/week during the school year and 40/week during the summer. Provide "Commercial Lobster" with the arrival estimate from the couriers. The number for "Commercial Lobster" is 617-946-3355.

****It usually takes about 1.5-2hrs for the crabs to arrive once you've ordered them. NOTE: They don't do rush delivery on Fridays because they're so busy so you will only be able to order crabs Monday-Thursday.