Small Polyp Scleractinia FAQ
v 1.4
by James A. Fox
Updated 03/31/04

Please note this is an ongoing project primarily focusing on (but not limited to) Acropora spp., which will be upgraded as I go along.  I am by no means an expert.  I do not have a degree in marine biology.  This basic FAQ is based on the knowledge I’ve accumulated by reading various books, my interaction with the online reef keeping community, and many years of experience both as a hobbyist and local fish store (LFS) employee.  These are not rules carved in stone to be followed to the letter but my opinion, which may differ from your viewpoint.  Also, note that I use the word coral throughout this text in the general sense, to identify a colony or colonies, not individual polyps.  Feel free to send email with suggestions for improvement.

1. Do I have enough light to keep Acropora?  How many watts per gallon are needed?  Watts per gallon (w/g) is not a very good method of determining light requirements.  Following this "rule of thumb", 100 watts over a five-gallon tank (20w/g) appears much better than that same 100 watts over a ten-gallon tank (10w/g), but the intensity is lacking in both cases.  One hundred watts is still one hundred watts, no matter how you slice it.  Intensity is the key, the more the better.  To paraphrase a recent post by Eric Borneman, “if a coral, for example, requires 15,000 lux to saturate, it needs to get that amount of light regardless of tank size.  So, if a 175 watt metal halide puts out 17,500 lux at the water surface and 8,000 lux ten inches down, it’s enough light for the coral at the surface but not at the bottom.”  Read on…
2. Do I need metal halide lighting, will VHO/PC lighting do?  Personally I am a great fan of halide lighting, so my opinion is biased.  When approached with this question, I recommend 250w halides minimum, with 400w halides being all the better.  Can you get away with VHO/PC (or even 175w halide) lighting?  Sure, many people do.  Do I think it’s the best for the coral?  No.  Most species see extremely intense sunlight under natural conditions.  We should try to mimic this as best we can, and I don’t believe anything less than 250w halides will do.  For more information on lighting, refer to “Shedding Light On The Reef” by Richard Harker.
3. What about water parameters (salinity, calcium, alkalinity, phosphate, nitrate, etc.)?  Obviously nitrite and ammonia should be undetectable.  Nitrate should be as low as possible (<10 mg/L).  Phosphate should be <0.04 mg/L, as anything greater will promote nuisance algae growth.  Salinity should be maintained at 35 PPT (~1.026).  Temperature is currently a subject of hot debate.  Many people have successfully maintained aquariums at ~77°f (25°c), others at 84-86°f (~29-30°c).  I will not get into this debate here.  However, I maintain my aquarium at 82°f (27.8°c) with great success.  For calcium and alkalinity natural saltwater levels (NSW) should be your goal (420 mg/L Ca, and 2.9 mEq/L (8° dKH) alk {TMCRA Vol.1 Fosså and Nilsen 1996}).  To encourage coralline algae growth, I like to maintain an elevated alkalinity level.  Levels as high as 3.6-4.3 mEq/L (10-12° dKH) should be fine.
4. How much water motion and what type are needed?  Coral use water flow (most importantly) for gas exchange, to remove waste, and to bring food.  Without this, the coral could easily suffocate or starve.  Consider these coral are normally exposed to crashing waves, strong currents and/or tidal flows.  For these reasons, since it is virtually impossible to duplicate this situation within the confines of an aquarium, I believe you can never have enough water movement.  Volume and alternating motion of flow are (in my opinion) equally important.  As with light, the more you provide the better.  However, you do not want to aim (for example) a power head directly at the coral.  Let indirect motion create the needed flow.
5. Do I need to feed these coral? Yes, absolutely!  Maybe not directly per se, but indirectly via the water column, or through a natural supply of plankton (zoo and phyto).  This can be accomplished by occasionally cleaning the glass of algae, and with the addition of various prepared foods (“Spray Dried Phytoplankton”, “Golden Pearls”, etc.), fresh or frozen phytoplankton (“DT’s”, “Instant Algae”, etc.), among other homemade recipes.  This feeds the infauna, which will breed and in turn provide food for the coral.  Be sure to gradually ramp up the amount of food offered.
6. I have a picture; can you identify this Acropora?  In a word, no.  Comparing the coral to pictures found in books, is not an accurate method of identification.  You may come close, but it would be guess work at best.  Too many species are strikingly similar.  Many things affect growth formation and coloration (such as lighting, water motion, placement, etc.).  Coral in a natural environment will have different growth patterns and coloration then the same coral grown in an aquarium.  Also small frags would not display as many natural characteristics as a more mature colony would.  One would have to cut a fragment, kill and remove the tissue, and examine the skeletal structure for proper identification at the species level.
7. How about coral placement in relation to one another?  Careful consideration should be given in this area.  Overcrowding and territorial disputes are usually dealt with via chemical warfare (a major stressor), possibly promoting bleaching events, or even rapid tissue necrosis (RTN).  Once RTN begins, the affected coral succumbs within a matter of hours (not days as is often believed) and it can quickly spread to other colonies.  Immediate action must be taken.  More often than not you will end up having to frag the unaffected branches or entire colonies will be lost.  A situation best avoided, and a strong argument for providing plenty of breathing room between colonies.  Regular carbon use can help to remove this chemical stress before RTN sets in.  Another method of territorial domination is growing over (i.e. plating) a coral mounted at a lower level, effectively shielding it from light.  The fix for this is simply to frag the offending coral.  Allow plenty of room for growth in every direction.  For more information read “Toward Success with SPS Corals” by Terry Siegel.
8. How long after initially setting up the tank, should I wait before adding SPS?  In my experience, these types of coral require a more mature, well-established system.  After the initial nitrogen cycle, there will be multiple algae growth phases.  Once you get beyond this, you should be able to safely introduce your first coral.  This timetable usually falls between the first six to twelve months.  Although it’s been said many times, it’s a saying well worth repeating…nothing good happens quickly, when it comes to reefkeeping.  Be sure to gradually introduce coral to your system.  Do not try to add a box of coral all at once, especially with smaller aquariums (less than 120 gallons).  Allow time for your tank to adjust to the increased bio-load after each addition.
9. How should I acclimate my new addition?  Some may find this method to be extreme, but I prefer to err on the side of caution.  After all, the last thing I want to do is lose my latest acquisition!  For the most part this will take about two hours, but sometimes less depending upon how far apart bag and tank water parameters are.  First add the bag water and coral to an old salt bucket (or other appropriate container), and then test this water for salinity and pH.  The further these readings are from the tank’s water parameters, the longer the acclimation period.  Next start a slow drip of 1-3 drops per second (using airline tubing) from the tank to the bucket.  Keeping in mind that most SPS (some more than others) will produce an excessive amount of slime when stressed, add a small powerhead to the bucket, in order to create enough circulation so as to prevent a slime buildup around the coral.  Again, do NOT aim the powerhead directly at the coral!  Occasionally remove a cup or two of water from the bucket and discard.  When you feel enough time has elapsed that the bucket water and tank water parameters are the same, you can add the coral to the tank.  The method I have just described has worked well for me.  It is by no means the final word on acclimation.
10. Can I mix SPS with soft coral?  Certain soft corals (especially Discosoma and Actinodiscus) pack quite a punch (toxicity) and can easily overwhelm many (if not most) stony coral either through chemical warfare or direct physical contact. As an example, several leather coral (Sinularia spp. and Sarcophyton spp.) are believed to release chemical compounds (growth inhibitors?), which can affect surrounding coral (in particular certain Acropora spp. and Porites spp.) negatively.  Quoting from Aquarium Corals by Eric Borneman under the topic Husbandry Considerations (page 112), "The obvious zonations that occur in the wild should be carefully considered, and it is in the coral keeper's interest to have soft corals and hard corals minimally intermixed, if at all."  If one takes the proper precautions it can be done, but I don't recommend it.