By Bob Goemans
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Bob Goemans corresponds with David Lim (Malaysia)

David Lim (Malaysia) writes...

Dear Bob,

I have been maintaining a 120-gallon SPS dominated aquarium for only eight months. This tank has a bare base (no sand bed) with live rock structures. For my initial setup, I used 70% of seawater taken directly from the sea nearby, and 30% from an old aquarium. It has 13 fish, and as for the inverts, 80% is SPS and 20% are LPS.

I use two 14K, 250W, Hamilton MH bulbs, four 54W ATI T5 actinic tubes, two Tunze pumps (7094 model) with external electronic control for circulation, and two return pumps.

Filtration consists of one 25-gallon sump (plenum system) with H&S protein skimmer, phosphate reactor and activated carbon.

I recently changed to a new DIY calcium reactor because the old one cannot maintain enough alkalinity and calcium.

Water parameters: pH 8.2, dKH 9, Ca 400, magnesium 1350, Phosphate undetected, Nitrate none and no obvious algae nuisance is found in the aquarium.

For the first few months, the color of my corals especially SPS in my tank were doing well, but, after that, some SPS are getting faded.

Please advise why some of my Acropora are faded in colour, - is it due to my MH bulbs being too old (about one year since I have taken them from my old LPS tank)?

Your prompt reply to the above will be much appreciated.

Thank you,

David Lim


Bob replies...

Dear David,

Thank you for your letter, and I must say your water parameters appear to be excellent, as is your equipment. Since you do not mention the coral species being maintained, or their placement in your aquarium, I would say that ‘lighting’ would most likely be the culprit. In fact, the overall quality of light reaching shallow water coral specimens taken from the wild is always less in the aquarium than it was in the wild.

Even though your lamps were probably originally sufficient to maintain most species coloration, their spectral quality and no doubt intensity has subsided somewhat since then. And if no longer sufficient, corals tend to increase their zooxanthellae content, which is a brown colored alga, thereby changing their coloration to a more brownish tone. Also, depending upon species and where collected, those in the aquarium may be experiencing a reduction in UV, which will also affect their coloration.

Therefore, it may well be new lamps are needed, and where some coral species are concerned, a 400W lamp may be needed if trying to maintain Acropora species that were originally found in ‘very’ shallow waters.

Hope this helps,



Lighting; Coral Color

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