j.falk
Valuable Member
It was my HOB filter. I used to leave it on while feeding frozen fish food and some of the food would get sucked up into it and subsequently broken down which would add nitrates/phosphates to the water. From my understanding, nitrates and phosphates fuel growth in corals, coralline and algae. When my filter was left on 24/7 my corals and coralline growth was crazy...it looked like my softies were growing overnight.
A couple months ago, I read online where people were shutting off their HOB filters while feeding to allow the fish/inverts a better chance of getting food...so naturally, I decided to try it too. It worked...all the food was being eaten and none of it was going into the filter anymore. Good, right?
Wrong.
After that, when I would go to do the weekly cleanings of my filter, I noticed that the filter floss was looking clean...it barely had anything in it...so I thought things were going good. The fish and inverts were getting all of the food and the filter wasn't getting gummed up with leftover food and polluting the water...that seemed like a win to me.
Fast forward a month and my tank is staying really clean. I rarely ever have to scrape algae off the glass, the sand is staying nice and white and the fish are fat and happy...but my corals are no longer growing like they used to. In fact, it almost seems like everything has stopped growing completely.
Then a snail died, one of my first nerites...the biggest one in fact...and I thought, it must be old age...I've had it for over a year so maybe they don't live that long. Not a big deal.
Then the next week, one of my spiny ninja star snails died...same thing...I thought it was old age. I bought it at the same time as the nerites so I assumed it was old too. Darn, that sucks...another one died.
Then the next week one of my Astrea snails died...biggest one...didn't think much of it...figured it was probably old age too.
This week I found two more Astrea snails belly up on the bottom of the tank not moving...one ended up surviving and one appears to be on it's way out. Not eating, not moving...just sitting there.
That got me thinking...what has changed with my tank that would cause all of my biggest snails to keep dying one after another?
So I sat down and really looked over the tank. Everything looked fine at first glance...but then I noticed that the coralline had died off in a lot of places. What was once thickly covered purple rock was now barren and white. I had recently added a bag of sand to the tank and the last time I did that in a previous tank, my coralline had died off so I thought maybe that was it...hence my first response to this thread.
After posting that, I then noticed (a few days later) that the thick green algae growing on my back glass that was always covered in pods had died off too and that my sand bed had three patches of dark brown spots in it...which are the beginning of dinos. I know this from lots of experience with dinos.
And that's when I finally put two and two together...shutting the filter off was prohibitive as the leftover over food that was being collected and broken down to fuel growth was no longer there. My nitrates and phosphates had dropped, algae had died off, coralline was dying off, dinos were starting, and my corals were no longer growing. What I thought was me adding a bag of new sand to the tank causing problems turned out to be not the right guess.
Since then I have upped my feedings of the tank and am now leaving the filter on again. The dinos that were once 3 different patches on the sand are now down to one small area and my corals are looking healthy again. I'm assuming I'm back on the right path with things but it's mindblowing how something so simple could have such a profound effect on my entire tank ecosystem.
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