minimum light for acropora

Discussion in 'SPS Corals' started by Atilla, 16 Aug 2009.

  1. Atilla

    Atilla Sponsor

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    hey guys

    this thread is not intended to keep corals with minimum light.

    about a month ago i placed 4 very small acropora frags in a refugium under normal T8 and they are starting to encrust. There are just 4 tubes (2 blue and 2 white).

    Now my question is this...what would be the absolute minimum light to keep acroporas alive and well. these frags are alive and encrust very slowly and are obviously not growing fast.
     
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  3. Tony

    Tony

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    SPS can be kept under T5's with no problem. The minimum lighting necessary is hard to determine as it depends on numerous factors like tank depth, the placement of the corals high or low in the tank, the quality of bulb as one would need less high quality bulbs then poor quality bulbs and lastly the type of coral as some SPS's require more light than others and they don't all need to be under blinding light. You seem to be keeping your corals happy as they are growing so your lighting is sufficient. Look to your animals for indicators and not statistics
     
  4. Atilla

    Atilla Thread Starter Sponsor

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    thaks for the info tony. But i think im not explaining lekke...

    i run 250W metal halides on my dt, but i have a soft coral frag tank with some T8, and the acroporas are actually growing under them!!! this is not really normal?
     
  5. Mekaeel

    Mekaeel Moderator MASA Contributor

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    Atilla. I gues the reason why your Acro's are thriving is because they are very close to the lights. Also, water clarity plays a huge role here. If the water is clear (eg.due to the use of carbon), it will allow better light penetration.
    NB. guys. I am not encouraging the use of T8's for SPS!
     
  6. Atilla

    Atilla Thread Starter Sponsor

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    please understand i also dont encourage t8 fr sps! was just weird seeing them grow under there:thumbup:
     
  7. Tony

    Tony

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    Maybe it's the colour spectrum of the T8 bulbs
     
  8. Bob the (reef)builder

    Bob the (reef)builder

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    Guys its about how much light (photosynthetically available radiation) or PAR, ie in the correct spectrum, that is reaching the coral.

    Talking in types of light is actually very vague. I'm sure that it is quite possible to burn acros under enough T8 bulbs with enough reflectors that are strategically placed.

    There are masses of factors that can cause Halides or any other type of light you like to not be enough, or too much. How far away from the coral, how deep is the water, are you using reflectors, what type, how clean is the water, how many lights are clustered above the coral, what power are they, what type are they, what balasts are they using, is there any reflection of light off surfaces or substrate.

    These are what I thought of just now, I'm sure this list can be doubled or quadrupled with a bit of thought.:)

    The way to see what a coral is receiving is with a PAR meter. Even a lux meter (pretty cheap) can be used if compared to par.

    "hey guys

    this thread is not intended to keep corals with minimum light.

    about a month ago i placed 4 very small acropora frags in a refugium under normal T8 and they are starting to encrust. There are just 4 tubes (2 blue and 2 white).

    Now my question is this...what would be the absolute minimum light to keep acroporas alive and well. these frags are alive and encrust very slowly and are obviously not growing fast."


    If your question was, what PAR value is the minimum required for a certain species, it would be answerable properly. (Although most of of us would be hard pressed to give a very accurate answer.:p)

    Either that or give us as many of the answers to the above variables as possible.

    I sound a little bit grumpy, I know, but I don't mean to be. I just want to give a little more insight into the complexities of what is a quite broad subject.:)

    Cheers

    Rob.
     
  9. seank

    seank

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    Because it is Monday???:lol::p
     
  10. Bob the (reef)builder

    Bob the (reef)builder

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    Maybe.:p
     
  11. trad

    trad Fish, thats the word!

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    Thanks for that Bob. I've actually been thinking about this for a while now cause my lights are very old although they have the strength probably not enough PAR. The end effect is i think my coral clolour is not that great although the growth is still good for some reason. I always thougth that the temperature was the only factor but PAR will also affect the coral colour
     
  12. Bob the (reef)builder

    Bob the (reef)builder

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    You seem a little unsure about how these things relate to each other Trad.

    When we say that the lights have "strength" or are strong enough we are saying that they have sufficient energy measured in this case as PAR. ie. the strength of the light as far as the coral is concerned is the same as PAR.

    The colour temperature of a bulb is the "average" of all the actual values of all the wavelengths of colour emitted by the bulb. It's colour is then compared to the colour emited by a theoretical "black body" of a particular type at different temperatures. ie If we heat this object to a temperature of 20 000k we will get a pretty blueish colour, at 10 000k it only gets to a white, slightly yellow colour.

    This temperature rating will help to see the colours that you wish in your corals. ie a high 20000k bulb will bring out the blues and greens in your corals and increase flouresence so they look more colourful but it is mostly just providing light in the spectrum you want reflected. If you want your pink corals to show up, a 6500k or 10000k will do much better.

    If you want your corals to actually be more colourful, you need them to:

    a) not screen the colours out with zooxanthelae, which they will do if they need them all to make food to give themselves energy in low light conditions. ie they need enough PAR (so they can photosynthesize.) The more light you supply, the less Zooxanthelae/brown cells they need to get their energy requirement.

    b)under bright light some of their colour is produced by UV protective pigments so some UV is good to enhance these.

    c) get enough other nutrition to produce these pigments for protection, or prey attraction etc.

    d) have corals that are capable of being colourful (many don't produce much colour at all).

    e) ensure that your inorganic nutrient load (esp Nitrates and Phosphates) in the tank are not too high as this will again lead to excess zooxanthellae in the corals thus screening the colour.

    The lights (Halides anyway) that produce the most PAR are in the 6500K range. These are fantastic and much cheaper if all you want is healthy corals, but you will loose a lot of the colour we all enjoy as it is screened out for our veiwing by yellow and red wavelengths which our eyes see more easily.

    I hope that this has helped, please ask if I have not explained myself properly.:)
     
  13. sunburst

    sunburst

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    minimum light for acropora -

    No definitive answer. However to summarise what has been mentioned above.


    Acropora is traditionally found in high energy shallow surf regions; which require huge amounts of PAR and water flow that us humble reefers could not dream of reproducing.

    However acros under lower energy light sources are now a common occurrence world wide. These tanks only became possible with nutrient control combined with healthy feeding. A conflict that up until recently, most reefers in the long run were not able to sustain.

    All corals including acros have an amazing ability to adapt to various light sources. As a general rule of thumb... metabolism would be controlled by the primary light source. ie if halides and T8'S were run in tandem the T8' s would have little if any beneficial value. And if T8,S were the only light source then you give the poor buggers little choice.


     
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