Nutrition Part 1: Phytoplankton.
As larval animals and the small foods they require, rotifers or artemia nauplii, are vulnerable to being pulled into filters it’s customary to raise them in a bare tank with no filtration. The larval tank will just have an air bubbler to help keep food and animals in suspension; by adding live phytoplankton to the system you gain a useful benefits. Phyto will help keep water conditions acceptable by utilising the larval wastes as nutrition, at the same time its presence means that the food items, rotifers, are able to feed on the phyto and stay in state of optimum enrichment.
One of the problems with culturing phytoplankton is its propensity to crash, resulting in the loss of the culture. So, although live may be better, its potential instability means it can leave you without any on hand just when you need it. For this reason I believe that preserved phytoplankton is a very useful product as it means you’ll never be caught short. Not to mention culturing plankton can be a time consuming pastime.
Conversely, you can’t co-culture with preserved plankton, for this task it has to be live. Personally I always keep preserved on hand for the convenience, these days only culturing live when undertaking a breeding project.
A Practical Guide to Culturing Phyto for Reef Use.
To culture plankton you can either buy equipment made for the job or improvise using the odds and ends that are usually to hand in an aquarist’s household.
You’ll need a number of 2-litre clear lemonade bottles), rigid airline tube, standard airline tube, air pump, a couple of air valves, 2 foot/18w fluorescent tube with ballast and reflector (a power compact or energy saver bulb could be used instead), 500ml live phyto as a starter culture, and phyto food based on Guillard’s F/2 nutrient media. If haven’t got access to phytoplankton locally you can purchase cultures of phyto in the form of an algal disc.
Split your starter culture between two 2-litre clear lemonade bottles, at room temperature and aerate briskly. There’s no need to use an air stone, rigid airline tubing will give the best results.
Make up 1-litre of water to a specific gravity of about 1.015; I mix full strength salt-water 60:40 with tap water. Dechlorinated tap water is OK for this application as any nitrate or phosphate can be considered to be additional nutrients for the phyto. Add 1ml phyto food to the mix and split this evenly between the two bottles; lastly, wrap a strip of filter floss around the airline to block the mouth of the bottle; this helps to limit the possibility of atmospheric contamination (this is essential when culturing Rotifers nearby). Repeat the addition of water and food daily until both the bottles are full.
When both of the bottles are full, I’d recommend starting a third culture. At this point suspend feeding bottle number one, this is the one you’ll start using in about six days time. Then more or less repeat the procedure you started with – use half the culture from bottle number two to start a third bottle, add another airline valve plus a length of flexible airline tubing connected to a length of rigid airline tubing to run the extra bottle, then top up both of these bottles with a litre of 1.015 s.g. salt water and feed each bottle with 2ml of phyto food. Don’t forget the strip of filter floss.
Proceeding in this way, you can expand your culture to whatever volume you want, bearing in mind the capacity of your air pump and whether you can sufficiently light the extra bottles.
Start using the phyto when it’s a rich green colour at around the six to nine day mark (somebody, I don’t recall who, once described it as being ready when it looks like “Kermit in a blender!”); say 500ml per day from bottle one. When your phyto culture is down to the volume you started with repeat the feeding process.
Periodically you’ll need to either clean your culture bottles with a bottlebrush to remove green slime build up or replace them with fresh ones, for the hobbyist this is an advantage of using lemonade bottles over dedicated phyto reactors.
Phyto can and does “crash”, this is where your lovely green culture can go clear overnight and become useless. Crashes can be caused by a number of different factors – temperature, airflow, and contamination being the most likely probable causes. Symptoms to look out for are clumping or plating, this where the culture becomes “lumpy”, you may be able to save a culture that does this by pouring it through a net and then restarting it. Another phenomenon to look out for is where your culture gradually loses colour over a couple of days, this is contamination – something is eating all that lovely phyto, usually you’ll find that if you look carefully you’ll see a burgeoning population of rotifers or brine shrimp. If you’re desperate for green water you could try pouring the culture through a rotifer net and then restarting it, otherwise I’d be tempted to just use it as an extra zooplankton culture.
If one of your cultures does crash it’s worth trying shaking the bottle vigorously (don’t forget to put a top on or you’ll “green wash” your room) or even blowing into the bottle yourself. It’s possible the pH of the culture has risen as it’s used up the available carbon dioxide; by shaking or blowing into the culture you’re reintroducing the CO2 hence reducing the pH. Once you’ve done this, restart the culture, sometimes this will allow it to recover. If you do successfully recover the culture it may well mean you need to increase your airflow; don’t forget that apart from keeping the phytoplankton in suspension, the air bubbles you are introducing bring with them small amounts of CO2, and that this CO2 is needed for photosynthesis; indeed commercial farming of phytoplankton will often incorporate carbon dioxide injection into the process.
A tip here is to try using carbonated mineral water (not lemonade!); it sorts out low CO2 problems a treat!
The problem of contamination is particularly real if you’re culturing rotifers nearby, and especially if you suffer brain-fade when doing routine culture maintenance. ALWAYS work on your phyto cultures before attending to rotifer cultures – otherwise your phyto has a tendency to turn into zooplankton! And always keep rotifer cultures and phytoplankton cultures well separated, in different rooms if possible, if not, then on opposite sides of the room. If you’re stuck for space try to minimise the possibility of contamination by having the phyto above the rotifers.
Starting a culture from an algal disc.
Algal discs contain an agar substrate on which a pure culture of micro-algae has been grown. To start off from a disc firstly remove the seal from the disc, then add enough sterile water to the disc to cover the culture, replace the cover and place under a white light for twenty-four hours. At the end of this time loosen the cells of phytoplankton from the surface of the culture by rubbing with a clean finger or Q- tip, then pour the cells along with the water into 500ml of saltwater, made up to around 1.105 SG. Split this mix between two 2-litre bottles then add a further 500ml of saltwater, along with 1ml of phyto food, to each bottle. Then just continue with the same process as outlined earlier.
Sterile water can be obtained by boiling or micro-waving water which is then allowed to cool to room temperature With commercially prepared algae cultures you always get a lot of emphasis on using sterile water, sterile containers, and sterile equipment. While this may be of great importance in commercial aquaculture, it’s not as important when it comes to feeding a reef. Any bacterial contaminant is most likely to be treated as just another food source by the animals we keep in our reefs.
Lighting for phytoplankton.
Phyto are not too fussy about the type of lighting used. Generally I’d say daylight rating lamps, around 6,500 Kelvin, would be your best choice, but in nearly any white light will do. Similarly, when it comes to quantity of light used, the greater amount of wattage used the faster phytoplankton will grow, but for the hobbyist, again, most lamps will do the job. I find I can culture up to 6 – 2-litre bottles or 5 –3-litre bottles in front of a single 2ft long, 18w fluorescent lamp (with reflector) mounted horizontally. One tip is to use old tubes that’re past are their best for reef tank use, they’ll still give good results with phyto.
The photoperiod, the length of time the culture’s lit for, can be between 16 hours and 24 hours a day. will be fine. Twenty four hour lighting might be of concern for other animals in the vicinity of your phyto culture station, so it may be worth shielding the light from the rest of the room. I’ve used plastic mirror tiles for this in the past, which has the benefit of increasing the amount of light available to the cultures. I wouldn’t worry too much about the amount of light spilling over near your reef, light from sumps and phyto probably represents no more than the amount of light available on the reef at night.
Recommended reading: -
Clownfishes by Joyce D. Wilkerson published by Microcosm.
This is a practical common sense read that presents information on plankton culture in a friendly, accessible manner. Also a must have if you intend to try rearing clowns.
Plankton Culture Manual by F.H. Hoff published by Florida Aqua Farms.
This is a much more scientific treatment of the subject. If you want to learn about phytoplankton in depth go for this book, though it may be a difficult read if you’ve no scientific background.
©2006 – 2009