The AK Culturi-S is the smaller reactor in the Culturi range, sized for 1 L phytoplankton cultures. The sealed glass vessel, integrated light, and gate-valve airflow all match the larger Culturi-M, just at a smaller working volume.
It works well as a first reactor for a single strain, or as a stable backup feeder running alongside an existing culture. For box contents and specifications, see the product page.
The glass vessel is not fixed to the base unit, it is held in only by friction. Please ensure you show extreme care similar to how you would treat any glass equipment.
This unit contains multiple glass components. Handle all glass parts with extreme care, including the rigid glass tubing and the glass vessel, to avoid injury or damage.
When inserting the rigid tubing into the seal, lubricant is usually not required. In most cases, the tubing should slide into place with only very light pressure, about the weight of one or two fingers. Insert it slowly and stop when the end of the tubing is approximately one finger width above the bottom of the vessel. Forcing it too far or too quickly may fracture the base of the vessel and may also damage the light unit.
If additional slip is needed, use a food safe lubricant such as USP or food grade glycerin, or a small amount of sterile water based lubricant. Cooking oil should only be used as a last resort.
Because the vessel may be filled with water during use, any fracture could also result in water damage to the light unit and surrounding area if proper care is not taken.
After installation, thoroughly wipe the tubing clean on both the inside and outside of the vessel to remove any lubricant residue before use.
WARNING: It is highly advised that the rigid tubing is removed before removing the lid from the vessel. This is especially important if you are using the Pod Core as you may risk damaging the tubing or vessel and potentially injuring yourself if any glass were to break.
Good, clean cultures are not possible without good, clean sterilisation. Massively reduce risks of cultures crashing by sterilising at every opportunity.
There are a few different options for sterilisation ranging from simple and safe, to extremely effective but potentially dangerous to your skin and eyes.
We'll stick with the simple and safe ones here, but if you're confident we do recommend researching tougher methods.
White Vinegar
Diluted Isopropyl Alcohol
Isopropyl alcohol makes for effective sterilisation, If you have 100% isopropyl alcohol it is recommended to dilute it with water to 70% to prevent it evaporating before it can even become effective.
Avoid adding boiling water to the vessel, or rapidly changing the vessel's temperature as it may fracture the glass.
We highly recommend synthetic salt as you will not have to sterilise the water. If you only have natural seawater as an option we highly recommend sterilising it also so that any microorganisms it hosts don't consume what you're trying to grow.
If you intend to use natural seawater, we recommend neutralising life inside it with chlorine, and then neutralising the chlorine with thiosulphate, you've done it right if you can smell chlorine before, but not after adding thiosulphate.
You should attempt to match the salinity of the starter culture you have, you could consult your supplier for the exact specific gravity, or in most circumstances, 1.022-1.026sg (30-35ppt) suits most strains. Some strains prefer the lower end of that range, others the higher end. The Lighting & Salinity section lists the values we recommend per strain.
Please refer to the "Preparing Saltwater" section above before continuing...
Once you have your saltwater prepared, fill the glass vessel up with 900 mL of clean fresh saltwater. You will need the remaining volume for adding your starter culture.
For fertiliser, you will want to use Guillard's F/2 for most strains (e.g. nannochloropsis, tetraselmis). Follow the instructions carefully adding the required amount to your glass vessel, do not stir with anything that hasn't been appropriately sterilised.
It's a good idea to ensure the fertiliser is well distributed within the water before continuing on with the next step, simply stir the water or swirl the vessel carefully - though not doing this may not be detrimental to the success of your culture we do recommend it to prevent any concentrated amounts of fertiliser damaging sensitive cell walls.
To give an exact amount of how much phytoplankton you need to begin a culture, would be: 1 single cell.
That's correct, that's all it takes, we do highly recommend adding more though with a 9:1 water-to-starter-culture ratio being the safe margin.For the Culturi-S that means 900 mL saltwater with 100 mL starter culture (a generous start, you'd likely still succeed with 25 mL)
Turn on the unit's integrated light if you haven't already and add your desired starting amount.
Phytoplankton generally performs best under strong aeration. Turn on the air pump, then open the gate valve attached to the rigid tubing fully, or as far as it will allow, to provide a high level of airflow. This helps keep the culture well mixed, improves gas exchange, and prevents cells from settling at the bottom. For most common phytoplankton strains, this level of airflow is suitable and supports consistent growth.
If everything was done correctly, your phytoplankton will begin to darken, often slowly for the first day or two, then quite noticeably day after day from there.
Keep the water between 18-25°C (64-77°F). Above 26°C the culture will stress, so if it is climbing too high, lower the brightness to reduce the heat from the light.
If you find that it is growing too quickly, lower the amount of time it receives light, and do the opposite if it's growing too slowly.
You may experiment with adding more fertiliser to achieve your desired density.
Depending on your light schedule and brightness, you may reach the harvest point earlier than shown below, in that case, you should harvest as soon as possible.
Highest density and maximum health is typically found around the 5th and 7th day. Simply pour the contents of the vessel into a clean 2 L bottle and store it in the fridge unless you intend to use it immediately. (refrigeration prolongs life significantly). Keep the amount of time the phytoplankton is exposed to air at a minimum. Avoid collecting dead or dying cells that rest at the bottom of the culture, healthy phytoplankton will be in the water column.
After every harvest you should reset the culture back to the beginning by sterilising everything. It may seem unnecessary but it is paramount to eradicate any airborne bacteria that may have made it's way in before it begins to thrive on your sequential cultures.
Based on our experience, neglecting to properly reset is starting the clock on your culture's downfall.
After properly cleaning everything, repeat the process from Step 1: Filling up.
If you are having trouble getting a stable batch going, it helps to step back and remember that phytoplankton is a very simple organism with very simple requirements. Before looking for complicated explanations, start with the fundamentals.
Here are the most common causes of phytoplankton culture failure based on our own experience.
Contamination
The air around us contains bacteria and other microorganisms, and some of them can compete with phytoplankton for the same nutrients needed for growth. If equipment is not properly sterilised, or if the culture is exposed to too much unfiltered air, contamination can gradually build with each harvest. Over time, the culture can become increasingly impure until it is heavily contaminated, crashes, or is no longer a healthy phytoplankton culture.
In some cases, green cyanobacteria may be mistaken for phytoplankton without microscopic analysis. Excessive cloudiness can also be a sign of a bacterial bloom rather than healthy culture density.
Air drying is not recommended. Once equipment has been cleaned and sterilised, it should be kept as clean as possible and used in a way that minimizes reintroduction of contamination.
Unless you are working in an extremely controlled environment, some level of bacterial presence is inevitable. The goal is not absolute sterility, but to keep contamination low enough that the phytoplankton can continue to outcompete it. For this reason, it is also wise to retain a small portion of an earlier, cleaner harvest as a backup in case the main culture begins to decline.
Water Source
Using anything other than properly prepared synthetic saltwater carries additional risk. Natural seawater and aquarium water can introduce unwanted bacteria, organics, or competing organisms. These sources should not be used unless they have been chemically sterilised, as there is no practical substitute for properly sterilising non-synthetic saltwater before use.
Temperature
Most commonly cultured strains will begin to slow down, become stressed, or start to decline once temperatures rise beyond 26°C (78.8°F). Prolonged exposure at or above this range can become lethal. A temperature range of 18 to 25°C (64.4 to 77°F) is generally ideal for stable growth.
Other possible causes
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