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Our Recirculating System

The main recirculating system housing the majority of our colony has a large sump with biological media, a Reverse Osmosis (RO) system supplying water to the tanks, carbon filtration, a drum filter for mechanical filtration, UV lights, a heater, and monitoring and dosing systems for water quality. See the Maintenance section for information on how we clean and maintain the system.

Large sump contains biological media

RO system supplies water


Drum filter at the bottom left, carbon filter and canister filter on bottom right. Monitoring unit on wall above.


Dosing systems are controlled by the monitoring unit, and dose sodium bicarb to maintina pH, and salts to maintain conductivity.

Advantages of a Recirculating Water System:

Monitoring and Dosing System

We find the monitoring and dosing systems to be invaluable in maintaining our system water stability, as well as in reducing labor. The temperature, pH, and conductivity are monitored. There is capability to monitor dissolved oxygen and redox potential, but we do not have these set up. Manual water quality is performed once a week, to confirm the monitoring system is functioning properly.

The monitoring system allows us to set an acceptable range for each parameter in the system. If the temperature falls outside the set range, the system alarms. The alarm is connected to an email and phone system, so a lab member is alerted. This is very useful if an alarm occurs during the weekend or evening hours.

If the pH or conductivity falls outside the normal range, the dosing system is triggered. Sodium bicarbonate is added to buffer pH, and/or marine salts to maintain appropriate conductivity. If the conductivity reading continues to fall despite the dosing, the alarm is triggered, and a lab member is alerted. The alarm will stop when the reading returns to the normal range. Note: We find the Reef Crystal salts (Instant Ocean) supplied by Aquatic Ecosystems to be a superior marine salt to the product otherwise shipped. Specify “Reef Crystal” when ordering.

Overall, we recommend the monitoring and dosing systems to anyone considering a recirculating system. The initial added cost will pay itself back many times in terms of reduced labor in water quality management, and more importantly in preventing loss and illness of important animals.

Drum Filter

Another advantage of this system is the drum filter. It provides very good filtering of solid waste carried in the water. It requires little maintenance, as it is changed/serviced by Aquatic Ecosystems annually. The amount of waste generated by the frogs remains a problem in other areas however, as outlined in the Disadvantages section following.

Dual Pumps

The system is supplied with two water pumps, shown below. This is an advantage for several reasons. We switch the in use pump each month, extending the life of the pumps. Also, we have a back up in case one pump fails. Pump failure without a backup can cause serious problems. While adult frogs will likely do fine for a day or two in standing water, tadpoles will suffer from changes in water quality. Replacing the pump under stressful conditions (usually on a weekend during the evening when no physical plant staff are available) is something to be avoided in and of itself.


Other Advantages

The racks on this system allow placement of varied size tanks on any shelf, with the exception of the wet rack, which only allows for small tanks. This results in great flexibility and efficient use of space.

The racks are flexible enough to accommodate different tank sizes. Meduim sized tanks are shown here. The racks also accommodate taller tanks, as well as smaller ones if necessary.

The “wet rack” is designed for small 0.75 liter tanks. This allows us to maintain genetically valuable frogs as individuals or pairs.


Each tank on the wet rack houses one or two individual frogs. Tanks are labeled with lab tape, as well as small thermal printer labels. These labels are inside protective plastic covers, which are secured to the rack with Velcro. The labels remain secure, but can also be easily removed/replaced if necessary.

The water flow to the system can be controlled at many levels. Water can be turned on or off at the system, rack, row, or individual tank level. This is helpful when cleaning, and when organizing or moving tanks. Valves for individual wet racks can be seen to the left in the picture above.

The very large reservoir volume helps maintain stable water temperature, pH etc. This allows time to correct any problem before animals are severely affected.

The tank design does a good job of removing waste and keeping the frogs from escaping.

Disdvantages of Main Recirculating system:

The shape of the sump is not ideal. It is wide and flat, taking up a large portion of our frog room floorspace. A better design would be narrow and tall.

The main system tanks have a lot of drain and overflow drain parts, as shown in the picture below. These require a good deal of labor to clean. The tanks must be completely disassembled for washing, as the drain parts will warp in the dishwasher.


The wet rack tanks are fragile, and will easily crack or shatter if dropped. The mesh plug supplied with the tank tends to fall out easily, allowing the frogs to escape. We have modified each tank with a guard to prevent this, a laborious task. In addition, the lids warp over time, and can be dislodged. We use a heavy duty rubber bands around each tank to keep the lid on.This requires extra time and effort each time a tank is opened.

We replaced the standard circular mesh drain guard supplied with the wet rack tanks with a piece of rain gutter guard from the home improvement store. The mesh drain frequently became dislodged, allowing frogs to escape.The water supply lines to the wet rack tend to clog frequently, and the wet tray holding the tanks quickly becomes filled with debris, requiring frequent cleaning.

The tubes supplying water to the wet rack tanks, shown above right, frequently clog with debris carried in the water. This requires frequently unclogging the lines, using paper clips and various other homemade devices. Also, the trays the small tanks sit in become full of debris very quickly, and need frequent cleaning. Ideally, the debris should be swept out of the tray by the water flow, but due to it's sticky nature, it tends to adhere instead.

While the drum filter does a good job of filtering waste carried in the water, the main problem with any recirculating system housing frogs is removal of waste debris that settles out of the water in the system before reaching the filter. The sticky mixture of waste and skin sticks on and in every crevice and pipe, blocking tank outflows and drain pipes, and taxing the water filtration system. This has been our biggest source of labor investment and facility management problems.


We have made various modifications to the tanks to try to address the problem of waste accumulation, water quality and system maintenance. Our main modifications involve changes to the drainage and baffle systems of the tanks themselves. One example is removing the baffle included with some tank designs, and using a piece of plastic gutter guard from the home improvement store adhered to the back of the tank. This allows more waste to escape, yet prevents frogs getting out. The picture below shows this modification. The main drain and overflow pipe are on the right. We use plastic zip ties on all our larger tanks to hold down the back of the lid. The lids will otherwise eventually warp, and thus possibly become dislodged.


Preventing frog escape is another main issue. As previously mentioned, the small 0.75 liter wet rack tanks have with a mesh drain plug which readily falls out. We have modified these tanks with a piece of plastic screen glued in place of the plug (see picture above).

Waste management continues to be the main problem we deal with on a daily basis. You should expect no system you purchase will be perfect, and will likely require some type of modification on some level for your situation. You should also expect to spend significant time manually clearing the waste from tanks and pipes.