Grainger Lab X. tropicalis Tadpole Husbandry Protocol

Updated June 1, 2001

 

For raising tadpoles from fertilization to five days of age, refer to the Grainger Lab X. tropicalis Mating Protocol.

 

We are currently using a tadpole husbandry system created in collaboration with Will Brown, formerly of the National Aquarium in Baltimore. The purpose of this system is to raise tadpoles from a few days of age through metamorphosis with a minimum of "hands-on" effort and a maximal rate of survival.

 

The apparatus described herein are all easy to assemble and inexpensive – perfect if your lab is just getting started with trops or even if you already have a sizeable colony and are looking to expand.

 

Here we describe three setups: one for the care of large groups of tadpoles (the Gigaswamp), a simple and inexpensive one for taking care of medium sized groups (Dual-tank Biofilter) and a third for the care of small groups of precious, usually transgenic or mutant, animals (the Port-a-swamp).

 

 

1. The Gigaswamp

 

Transferring Tadpoles

 

Transferring tadpoles from tank to tank is perhaps the most perilous part of X. tropicalis husbandry. Tadpoles are particularly susceptible to shock from apparently minor changes in temperature, salinity, or pH, and these can kill large numbers of tadpoles in a matter of minutes. When transferring tadpoles from one environment to another it is always best to introduce them slowly. Allow the temperatures of the old and new container to equalize, and then transfer a small amount of water from the new container into the old. Repeat this process of adding water for several hours until the volume in the tadpoles' current container has almost doubled. Then pour the water containing the tads into the new container.

 

There are four critical factors to consider when raising young tadpoles: housing, density, cleaning and feeding.

 

Housing

 

The Gigaswamp consists of:

1. Two large, polypropylene tanks each of approximately 90-gallon capacity. One of these is the TADPOLE tank containing the animals and one is the SUPPLY tank holding water only.

 

2. The SUPPLY tank is filled 24 hours in advance to age the water. This ageing step is crucial to remove volatile contaminants from the water. Although we use non-chlorinated well water, we find that unaged well water is harmful to tadpoles. This may be due to dissolved CO2 in the water lowering the pH (incoming well water is about pH 5.8, well water aged one day in the SUPPLY tank is about pH 7). The water is recirculated using a heavy-duty aquarium pump (no carbon or ammonia filters are used with this unit) and is heated to 27°C by a 150W aquarium heater. Both the pump and heater can be purchased at a local pet store. The SUPPLY tank also contains several large rocks taken from a local stream and several sprigs of Pothos, or Devil's Ivy, that have taken root in the water. Before adding the Pothos to your setup, wash it thoroughly! Light is provided to both tanks by a standard 4-foot double fluorescent fixture, available at most home-improvement stores.

 

3. The TADPOLE tank contains some Pothos placed on floating styrofoam "islands" and a fluorescent light (as pictured above). The TADPOLE tank also contains a thick mat of green algae on the sides and floor of the tank (visible as a greenish tint to the water). We believe that this algae mat is a big reason behind the success of the gigaswamp. It not only provides an additional level of biological filtration, it also provides a more natural environment for the tadpoles. The water of the gigaswamp is teeming with microorganisms and algae and they love it.

 

4. Tadpoles can be raised through metamorphosis and even into early froglet stages in the Gigaswamp.

 

 

Cleaning

 

Text Box:  
Pump housing used to empty TADPOLE tank without sucking out tadpoles. 

We do not normally clean the TADPOLE tank for the first week after new tadples have been added. They seem to condition the water and don't do well if it is changed frequently. After the first week, change half the volume of the Gigaswamp every week. To do so, we use a submersible aquarium pump that is housed inside a large polypropylene bottle. The bottle has several large holes cut in the sides that are covered with Nitex mesh (Fisher) glued in place with non-­toxic aquarium glue. The mesh prevents tadpoles from being sucked into the pump. The output tube from the pump passes through a hole in the lid of the bottle and out of the tank to a floor drain. After emptying half the water, refill the TADPOLE tank from the SUPPLY tank. Finally, refill the SUPPLY tank from the tap.

 

Density

 

We start tadpoles in the Gigaswamp at a density of about 5 tadpoles/liter. This corresponds to about 1000 - 1250 tadpoles in 70 gallons (about 260 liters). At these densities, 75% of the tadpoles should begin metamorphosis (determined by the appearance of forelimb buds) at about 4.5 weeks of age and should become froglets by 6 weeks. Even faster times to metamorphosis have been obtained by lowering the density even further.

 

 

 

Feeding

 

For the first two weeks, we feed the tadpoles 4 or 5 times daily with SERA Micron (Sera North America, 1-800-755-7372). Start feeding with a small amount of food - just enough to cover the surface of the water with a thin, greenish film. Slowly increase the feeding frequency and amount as the tadpoles grow. A good rule of thumb is to allow the water to clear between feedings. After two weeks we use a mixture of SERA Micron and flake food (Aquatic Ecosystems, 1-877-347-4788 or 1-877-FISH-STUF) that we refer to as "Advanced Tadpole Diet". It is made up by combining 2 liters volume of "finely ground fish flakes" (Aquatic Ecosystems catalog #FOC), 1 liter volume of "45% protein fish food powder" (Aquatic Ecosystems catalog # F1A) and 34g Sera Micron (2, 17g jars). This mixture is high in protein and can be fed to older tadpoles or even froglets.

 

 

2. The Dual-tank Biofilter

 

This setup can be repeated as many times as desired to house any number of X. tropicalis. It is inexpensive, easy to set up, and self-contained. We use this system to raise tadpoles, froglets, and even adult frogs.

 

Transferring Tadpoles

 

Transferring tadpoles from tank to tank is perhaps the most perilous part of X. tropicalis husbandry. Tadpoles are particularly susceptible to shock from apparently minor changes in temperature, salinity, or pH, and these can kill large numbers of tadpoles in a matter of minutes. When transferring tadpoles from one environment to another it is always best to introduce them slowly. Allow the temperatures of the old and new container to equalize, and then transfer a small amount of water from the new container into the old. Repeat this process of adding water for several hours until the volume in the tadpoles' current container has almost doubled. Then pour the water containing the tads into the new container.

 

There are four critical factors to consider when raising young tadpoles: housing, density, cleaning and feeding.

    

Materials

 

NB: Many of these items can be purchased at your local pet store. Some items, such as glass tanks, are difficult to get by mail-order and usually HAVE to be bought locally. We purchased other items from either Aquatic Ecosystems (1-877-FISH-STUF) or from Pet Warehouse (1-800-443-1160).

 

2 glass aquaria, one (TADPOLE) ten gallon and one (BIOFILTER) five gallon capacity (bought locally)

1 submersible aquarium water pump and tubing (Aquatic Ecosystems catalog #PU14 for pump, tubing comes with Biowheel filter unit)

1 Marineland Biowheel filter unit (Aquatic Ecosystems catalog # BP3)

1 aquarium air pump, airstone and tubing (bought locally, airstone brand is Lee's Discard-a-Stone)

1 submersible aquarium heater (50W or 100W) with an internal thermostat (bought locally)

1 mesh bag containing shredded PVC for biofilter (Aquatic Ecosystems catalog # BF165 for mesh bag and #BF250 for PVC)

1 mesh fry tank to house pump (Pet Warehouse catalog #120766)

1 U-tube and plastic strainer for return siphon (Pet Warehouse catalog #439634 for U-tube, Aquatic Ecosystems catalog # PA1241 for plastic strainer)

A source of high-quality, dechlorinated water

 

Housing         

 

1. Place the BIOFILTER and TADPOLE tanks side by Text Box:  A dual-tank biofilter setup with the BIOFILTER tank to the left and the TADPOLE tank on the right. Although this particular setup houses froglets, we use it chiefly for tadpoles.

side. You can place several setups on one shelf of a sturdy metal rack (we use Metro racks: http://www.metro.com/ or 1-800-441-2714).

 

2. Place immerson heater (set for 25°C but not plugged in) in the BIOFILTER tank. Add mesh bag with shredded PVC and fry tank mounted on the side. Put aquarium pump in fry tank and connect to the Biowheel mounted on the side of the TADPOLE tank. The mesh fry tank housing keeps the pump mechanism from getting clogged with gunk from the water. Remove the fry tank periodically and rinse it off with distilled water.

 

3. Fill the BIOFILTER tank until it is almost full, then fill the TADPOLE tank to the same level. Place the plastic strainer on the end of the U-tube (some of the plastic may need to be trimmed away with a razor blade). Fill the U-tube with water and connect the two tanks, taking care not to break the column of water. Make sure the plastic strainer is in the TADPOLE tank to keep tadpoles from being sucked into the BIOFILTER tank.

 

4. Connect the airstone and tubing to the air pump and place one airstone in the BIOFILTER tank, being careful not to put it under the end of the U-tube (the bubbles of air will break the siphon and cause the tank to overflow). Place another airstone in the TADPOLE tank just at the surface of the water (we use Lee's Discard-a-Stone for this because it floats). Now turn on the heater, air pump and water pump. The water will be sucked from the TADPOLE tank by the siphon, passed through the BIOFILTER tank and returned via the aquarium pump.

 

 

 

 

 

Density

 

We start young tadpoles fairly dense, between 5 and 20 tadpoles/liter depending on the percent fertilization of the eggs. This translates to between 200 and 800 tadpoles per 10-gallon tank. They seem to do well at higher densities while young, between fertilization and about two weeks of age. After that, when the tadpoles are clearly growing, we split large groups into two or more tanks.

 

 

Cleaning

 

TADPOLE tanks are not cleaned, nor are they attached to the BIOFILTER tanks, until the tads are about 10 days old. Up until that time the tadpoles are too small to be retained by the strainer at the bottom of the U-tube and will be sucked into the BIOFILTER tank. However, make sure the airstone in the TADPOLE tank is working during that time – it's action helps to circulate the water when the pump isn't running. After 10 days, turn on the pump and start the siphon. At this point, cleaning is usually done once a week. To clean these setups, turn off the pump and disconnect the siphon. Drain the BIOFILTER tank and refill with clean water (we use the "aged" well water from the Gigaswamp SUPPLY tank). The reconnect the siphon and turn on the pump.

 

Feeding

 

Feed the tadpoles 4 or 5 times daily with SERA Micron. Start feeding with a very small amount of food - just enough to cover about half of the surface of the water with a thin, greenish film. Slowly increase the feeding frequency and amount as the tadpoles grow. A good rule of thumb is to allow the water to clear between feedings. The accumulation of a small amount of green algae on the walls and floor of the tank is normal and healthy, but avoid the formation of large carpets of green slime, as this is a sign of overfeeding. For tadpoles older than two weeks or so we supplement with "Advanced Tadpole Diet" (see above for the recipe).

 

 

3. The Port-a-Swamp

 

The port-a-swamp was developed largely by Lyle Zimmerman as a way to raise small numbers of precious animals on the bench-top (i.e. in plain sight where they can be watched carefully rather than downstairs in the animal room).

 

Text Box:  A port-a-swamp setup. The SUPPLY tank is on the right. Two boxes containing TADPOLE tanks of various sizes are on the left. This image illustrates the chief advantage of the port-a-swamp: observation of tadpoles is easy because they are located in the main lab. The key to the success of the port-a-swamp is observation. The tadpoles should be watched carefully, sick ones isolated quickly, and dead ones removed promptly. Care and monitoring should be done as often as possible, even on evenings and weekends.

 

Transferring Tadpoles

 

Tadpoles are particularly susceptible to shock from apparently minor changes in temperature, salinity, or pH, and these can kill large numbers of tadpoles in a matter of minutes. When transferring tadpoles from one environment to another it is always best to introduce them slowly. Allow the temperatures of the old and new container to equalize, and then transfer a small amount of water from the new container into the old. Repeat this process of adding water for several hours until the volume in the tadpoles' current container has almost doubled. Then pour the water containing the tads into the new container.

 

There are four critical factors to consider when raising young tadpoles: housing, density, cleaning and feeding.

 

 

 

Housing

 

The port-a-swamp consists of:

 

1. A SUPPLY tank (at the right in the photo above), usually a 10 or 20 gal. glass aquarium. See the above caveat about thoroughly cleaning all containers before use. This contains a standard-size aquarium pump for recirculating the water (no carbon or ammonia filters are used with this unit), a 50W aquarium heater to keep the water at 25°C, and some plant material - we use a couple of sprigs of Pothos, or devil's ivy. Again, before adding the Pothos to your setup, wash it thoroughly!

 

2. One or two large, flat plastic containers (we use two, 20 liter capacity sweater boxes from Wal-Mart seen at the left in the photo above) filled about 1/4 full with water and containing one 50W heater and an air bubbler to provide some circulation. These containers serve to maintain the temperature in the smaller, individual tanks placed inside them.

 

3. Small tanks, ranging in size from 0.05 to 1.5 liters. This assortment of tank sizes accomodates tadpoles of various ages at several different densities. We use 50ml. plastic fly vials (Carolina Biological Supply, 2700 York Road, Burlington, NC  27215, USA, 1- 800-334-5551) for single tadpoles. For several tadpoles, we use clear, plastic food service-type containers of about 300ml. capacity. It is important to purchase food-grade containers, since they should contain no harmful organic residues. We use ice-cube trays, which hold about 2 liters, for larger numbers of tadpoles. These are purchased at a local Wal-Mart. We put sprigs of Pothos in some tanks (be sure to wash it thoroughly), and aerate tanks holding 1 liter or more.

 

 

Density

 

Density ranges from 1 to 10 tadpoles/liter. In cases where only one or two tads are being raised in a single tank, we often add some water from a tank with other tadpoles (tadpole conditioned media or TCM). This seems to help with survival of single tadpoles, possibly by adding beneficial bacteria or some other necessary factor.

 

 

Text Box:  
A 2 liter TADPOLE tank containing about 40 young tadpoles.

Cleaning

 

Tanks should be cleaned once per week if they contain young tadpoles. Cleaning frequency and amount of water changed should slowly increase as the tadpoles grow. Generally, if the tadpoles are two weeks old or older, replace half the water once per day with water from the SUPPLY tank. Use a pipette to suck out bits of detritus, dead tadpoles, or large pieces of green slime.

 

 

Feeding

 

Feed the tadpoles 4 or 5 times daily with SERA Micron. Start feeding with a very small amount of food - just enough to cover the surface of the water with a thin, greenish film. Slowly increase the feeding frequency and amount as the tadpoles grow. Observe carefully and adjust the amount of food on a tank-by-tank basis. A good rule of thumb is to allow the water to clear between feedings. The accumulation of a small amount of green algae on the walls and floor of the tank is normal and healthy, but avoid the formation of large carpets of green slime, as this is a sign of overfeeding.

 

 

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