When you receive a new coral, chances are it's super happy and healthy. It has vibrant colors and full polyp extension. Hopefully, it's even better than you saw in the photo!
But, over time, maybe it starts to lose color. Maybe turn more pastel shades. Then, the polyps stop coming out so far. It doesn't die, it just doesn't look as good as when you got it.
Ever have that happen?
Sometimes, it occurs from the stress of transport and changing water conditions. Over time, it should recover.
However, if you're someone with stable water but still struggles to maintain the vibrance your coral arrived with, it may be that your water is too clean.
Coral needs food. Either direct feeding, broadcast, or sucking up what comes from the poop of the local fish population.
Yes, most coral get nutrients from photosynthesis via the colorful zooxanthellae in their flesh and absorb trace elements that come from your salt mix or additives. But, many corals also need to be fed regularly.
How much depends on what coral you have and your individual system. At the Cove, I feed our coral here twice daily with a regular schedule of frozen foods, Bulk Reef Supply's Reef Chili, and Red Sea Reef Energy.
I chalk it up to a low fish population relative to the amount of coral we have. No fish poop = less nitrates in the water.
Regardless, I base my need to feed on two metrics.
This is a lagging metric. In other words, the later result of our daily feeding process. If our coral is growing relatively fast with good color, I know we're on the right path.
Unfortunately, if something begins to go wrong, a decline in coral health usually comes long after the warning signs that we're either feeding too much or too little. So we make sure we pay attention to more immediate metrics.
Any time I've experienced coral color fade, it's been because my tank nitrates dropped to undetectable levels and I didn't catch it.
I know some hobbyists that struggles with high nitrates. I've never been in that camp.
Either way, knowing where your tank's nitrates are, in relation to what your coral prefer, is key.
We do this by testing our nitrates weekly.
We feed according to our regular schedule - our leading metric - and watch the weekly nitrate levels - our short-term lagging metric. We can then adjust our next week's feeding regimen based on how our nitrates are trending.
The ultimate lagging metric of beautiful, fast-growing coral is the result of this routine.
What is "Too Clean"?
Short answer, "too clean" is 0.0ppm nitrates in your water.
Your situation is unique. You may find that your corals begin to stress under 2ppm. Some people have healthy reef aquariums with nitrates in the 20's.
Generally, I'm in the camp that prefers low nitrates to having high nitrates.
I would rather feed good quality foods daily than have to implement nitrate mitigation efforts such as algae reactors, scrubbers, and refugiums or aggressive water changes.
Find what is right for you and your coral.
Would you rather feed your corals more often or have more fish and large refugium? No answer is wrong and there are certainly shades of gray in between. It's all about what fits your budget, schedule, and reef tank goals.