April 2 2011

Fresh water testing

Finally the whole system is set up and tested. It is running with freshwater as a test, and for rinsing the plastic. I am a little worried about how the different types of plastics will affect sensitive algal cells. But I guess I'll never find out, because there is no way for me to test that.

Some pictures of the work process

Cutting styrofoam for tank insulation.

Digging out all the pumps and other stuff from storage boxes.

My first tries at PVC glueing. Very fun! It is so fun it is clearly worth the money. PVC piping systems are just excellent. But watch the costs. There is no limit to how much you can spend on ball valves and unions.

Insulating hose for the chiller circuit.

An aquarist's great joy: Water on the floor ;-p. I used garden hose for the chiller loop. The connections between hose and PVC leaked. The same went for *all* the hose connectors for the two chillers. But most of the leaks could be fixed fortunately. Hopefully this is the last time I'll use garden hose in an aquarium project.

The main loop

The main loop is really the core in this system. It creates he flow between the two tanks. The construction is simple: A Maxijet 500 pump, a hose with a ball valve on. The drain is just a bulkhead with a piece of hose. The flow rate is essential to the functioning of the phyto fuge. A slow rate will be advantageous because it will allow more growth, which could be of great importance in the early phase, just after startup. It can also allow greater species variation. However, it could also limit growth at later stages, and will give a higher temperature in the refugium, since I don't have a separate cooling system for that. It is only cooled by the cold water from the display tank. Higher temperature in the refugium could potentially be good and bad. Good, because it allows faster growth. Bad, because it is unnatural to the organisms I keep. I want to aim for a compromise by keeping a temperature close to, but below 20 degrees celcius. The whole point of a continuous phyto growth system, or "photo bio reactor" as the official term is, is to have a flow that is low enough to not wash out plankton at a faster rate than it grows. I decided on a flow that is half the refugium volume per day. The refugum contains about 85 liters, so that gives 42.5 liters per day. I use a digital timer with 20 programs to let the Maxijet run for 1 minute 20 times a day. It must pump 2.1 liters each time. I tune it with the ball valve and by measuring the time it takes to fill a one liter cup. When the time is 28 seconds it is correctly adjusted.

The main loop: The green transparent hose goes up from the display tank. The bulkhead with two garden hose pieces is the return. A timer lets the pump run for 1 minute 20 times per day.


A Giesemann Razor 2 x 24 Watts T5 fixture, with Acradia plant tubes. I measured 15000 lux at the water surface.

Drilling holes for eye bolts.

Air pump

The task of this pump is to create water circulation in the refugium. I didn't want to use a water pump in case it damaged the plankton. I first wondered if it was necessary with any circulation at all. But given the fact that the water from the display tank is very cold, it will probably sink to the bottom. The lights will proably heat the surface water the most. These two effects could lead to unwanted stratification with nutrient or oxygen breach. Another issue with water stagnancy is that the algae concentration could be varying throughout the refugium. This will create errors when measuring concentrations, which form the basis for all calculations. So I decided to use an air pump for circulation. I inject the air into a tube that creates both a vertical and horizontal flow. It seems to work great. The horizontal flow makes it less probable that the water will only circulate in one part of the refugium.

Flow tube creating a small flow of water from the bottom to the surface with some horizontal movement too.

Skimmer with ozone

The skimmer is my Deltec APF600 from the 1000 liters system. I guess it is too big for this system. That wouldn't normally be a problem, but I don't want it to remove plankton from the display tank too fast. So I use a ball valve to regulate the flow through it. About 80 liters per hour is plenty. The skimmer will run all the time, but the ozone generator will only run for an hour or so per day. So I have it on a timer. More than that would be overkill in this small system. I am worried that the ozone can cause problems for my little plankton babies. But I have found a good solution for filtering the return water by letting it straight into a carbon reactor.

Solution for filtering ozone water from skimmer. The return water goes directly into this carbon reactor. It is currently empty since this is just a test run.

Ozone generator.


The chiller is only connected to the display tank. The temperature there is kept roughly the same as in nature. I ended up using my newest chiller, a Teco TR20. It works well, but the temperature shows as 2 degrees lower than on my handheld digital thermometer.

Teco TR20

My Aqua Medic Titan 1500 chiller had developed several leaks in the bulkheads to the heat exchanger. Really annoying, it is used less than 2 years in total. The old Aqua Medic chillers are some of the most expensive around, and poor quality too. Not recommended.

Chiller feed pump and return

These connections leaked a lot in the start. I really hope to use silicone hose next time.


As with most things in this project, it took quite some time to figure out wether I needed this or not. Saltwater contains a lot of bicarbonate, and some algae can take up carbon from that. Carbon dioxide on the other hand is more complicated to understand. But as far as I can tell, there is very little of it. Now, the question is if the algae will be able to grow on the bicarbonate. After a lot of reading I decided that I could not count on that. I need to provide the CO2. Calculations showed that given the low concentration of CO2 i air, there is no way that I can reach significant growth of phytoplankton only by diffusing air into the refugium. So I need to add CO2 specifically. I considered the yeast solution, but decided that it was time to invest in a real CO2 system. I thought about buying a CO2 bottle from an aquarium store, but the best I could get was an expensive, empty, 2 kilos bottle. 2 kilos is too little. Luckily there is a local fire tech company that sells used CO2 bottles to aquarists and beer makers. I got a filled 10 kilos bottle from them for less than what an empty 2 kilos bottle would cost from an aquarium supplier. It is 15 years old, and has probably been standing outside on a ship. But I think it looks sturdy enough. I bought the rest of the equipment from aquaristic.net in Germany. I considered going for a full solution with a controller and dosing pump for pH buffer. But that added a great cost, since I already own a good pH monitor from American Marine. I am not sure if that was a good idea or not. But I can always upgrade later. For now I will ontrol the solenoid valve with a timer that comes on 1 hour after the lights and goes off 1 hour before them. Not having a controller may limit the growth rate of the plankton, and require daily adjustments to CO2 flow. But manual adjustments may also give me a better look into the changes in growth rates.

10 kilos bottle. Should last awhile. Actually, it is only enough for 6 kilos of algae, dry weight ;-p.

The red hose is for CO2. It has a bubble counter and diffuser. The blue probe is the pH probe.

The Pinpoint pH monitor from American Marine. I am very impressed with this device. After storage for almost 2 years the probe was still within acceptable accuracy before I calibrated it. Everything about American Marine products give the impression of quality.

Solenoid valve for nightly shutoff of CO2.

Nutrient additives

One of the things that frustrated me about my last aquarium was the complete lack of control of nutrients. The pH was heavily buffered so there was no way to know if there was too little or too much CO2 available. I could measure nitrate and phosphate, but no trace elements. So when the growth rate changed for one of the many algae species I could only observe and do little. This time I decided to be completely scientific about it and use an organized method like the planted tank people do. Basically that means adding everything that the algae need in a proportioned manner, and measure nitrate and phosphate. To make sure that unused trace elements don't build up over time, water changes are performed regularly. The nutrients and relative proportions I wanted to use were those for the Guillard F/2 algae growth medium. I couldn't get that medium directly as nobody sells it in Europe, it seems. So I had to make my own. It was easy enough for nitrate, phosphate and silica, because I could buy those separately. But it was not that easy for the trace elements and vitamins. However, I was really lucky because I found out that a product called Seachem Flourish had everything in the F/2 trace element solution, and more. The proportions were acceptably close too. So I could just use that instead.

My additives: Nitrate, phosphate, Seachem Flourish (Contains about 28 different trace elements and vitamins) and silicate.

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