Decline in coral health?

[imclownfish]

Hello, we noticed a recent decline in coral health and wondering if anyone had ideas as to why. We noticed a couple weeks ago that first our SPS started to recede, followed by some decline in LPS health (less extension, not as puffy, death in the case of a Trumpet coral). However, when we placed some of the declining corals in our Coral QT, they instantly perked up the next day. One SPS frag that was dying in the main tank actually coloured up within a week in the QT tank. Another example is a space invader frag that was shrivelled to the point of showing skeleton tripled in size overnight in the Coral QT tank.

We can't figure out what is causing the decline in health in our main tank. The only thing we can think of is lower phosphate levels, but would that be something that a coral would be affected so severely by (IE, the space invader, become puffy again as soon as it was placed in the Coral QT tank?). We ran a poly filter to check for metals in the main tank, but it didn't pull anything out. The other thing is that we did have dinos for about 2 weeks prior to the decline, but the tank hasn't shown any sign of dinos for about 3 weeks now (we ran a UV filter which is not running anymore). Our parameters are as follows:
Main tank
8.15PH (Salifert)
7.9 DKH (Hannah)
<0.03ppm phosphate (Salifert)
8ppm Nitrates
1.024 Salinity

Coral QT Tank
8.15PH
7DKH (Hannah)
0.03-0.1ppm phosphate (Salifert)
1.024 Salinity

We are a little stumped, so any help or ideas would be appreciated. Thanks

 

[brmreefer]

Some things that I would consider if it were my system:

- I would check my daily swings - Temp daily high/low; Salinity High/Low
- The goal is stability.
- Re-check my test results to verify no testing errors - Things to consider: If using a refractometer, when was the last calibration and take a sample to a LFS or friend for testing to see their results.
- PAR differences between QT and DT - Is one significantly higher/lower.
- New dosing regimens being implemented that are causing drastic parameter changes - if so, then consider stopping briefly to see if there are any improvements.
- Tank inhabitants bothering corals - be sure to check nightly activities and that neighboring corals have enough space between each other.
- Newer tanks versus older (established) tanks if applicable. Newer systems sometimes need a little more time, but all systems age differently.

These were just a few thoughts that may help. Hope you figure it out and best of luck.