What's with my Monti Cap?

[Ocean Lotion]

Since I downsized from my 75 to a 30 bare bottom my monti cap gets covered with what looks lIke brown algae like the coral is dieing. I then do a water change and change out the media and carbon in the hob filter and the coral recovers. Nitrates are around 30. All other parameters are ok. What comes to your mind?

 

[Reefpuck]

Well nitrates are high...and now that you've lost your sandbed...you lost a lot of surface area for beneficial bacteria to grow and do it's thing (denitrification). I'm guessing you also removed a lot of rock during the downsize as well.

Lots of other things to consider, like what are your other parameters? I know you say they're good...but still helpful to post. I'm also guessing a new light...new flow...new filtration...new coral placement...etc? Lots of changes can shock a coral.

Hard to pinpoint with limited info.

 

[Ocean Lotion]

Wondering if anyone has had their monti cap look like this.