I've experienced this before. I was having the same issues you mentioned in your first post. <br>
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Pale SPS with little to no growth and non existent polyp extension. I finally came to the realization that my tank most be nutrient deprived. I was starving my tank and more importantly my corals. I started using Pohl's Coral Vitalizer and Xtra and went back to spot feeding them every 3-4 days and within a few weeks I have already seen a huge improvement. <br>
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Long version:<br>
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My tank is a 75g display tank with a 30g sump. In Sept of last year after over feeding and horrible husbandry, my tank experienced very bad cyanobacteria and bubble algae that would not go away. This prompted me to be over vigilant in making sure I got kept pristine water conditions. <br>
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Over some time, here is what I was doing and what I think contributed to it:<br>
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Upgraded skimmer, now rated for up to 300g instead of the 100g one I was running. <br>
Added BRS Bio Pellets reactor<br>
Added Chemi Pure Elite (1 unit) - really helped get rid of the algae<br>
Added Carbon every month for 1 week only<br>
Added Purigen reactor<br>
Added Rowaphos reactor<br>
Added Cheato and grow light - really helped also<br>
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... a 'little' overkill, I know. <br>
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Finally after only feeding fish for long time and basically focusing on water quality, Phos (hanna) and Nitrate (salifert) tests read 0 for both. I was never able to get a reading other than 0.00 from the hanna checker. Calcium/Alkalinity/Mag were all within optimal parameters.<br>
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Around this same time I switched from metal halides to LED (back in March of this year) and my corals faded some then adjusted back. However a couple months after they colored back up I noticed they were all getting paler and no longer had polyp extension. I spoke with a few people who keep SPS and they suggested I feed my corals/tank more because I was starving them. <br>
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I took the carbon, purigen and bio pellets offline and started to feed again heavily at first while I monitored my parameters and did water changes, then scaled back.<br>
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I also found out my potassium was very depleted after testing it with a salifert test, so I started dosing that as well with the Brightwell supplement. <br>
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It's been just over a month of dosing potassium and spot feeding my corals. They are growing like crazy with awesome polyp extension and the colors continue to get better. I still monitor the phos and nitrates every week just to make sure. The phos is now usually between .02 and .05 and nitrates are just barely noticeable on the salifert test.<br>
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Hope this helps!