Well, it's been since December since a tank update - far far too long!
Not much exciting happened between December and about March. Corals kept growing and everything was looking great. In March 2011 I bought some frags from Green Marine and STUPIDLY did not QT them. Even though I didn't buy any montipora corals, I still managed to get an infection of monti eating nudibranchs. These are the only items I added to the tank, so I know that the nudibranchs must have come with these frags. Anyhow, I started to see montis getting eaten - the first was very large pieces of tyree blue polyped tank base monti cap. The pieces, which were about 8" long and 4" wide are completely dead now. I found many nudibranchs and eggs on the dead pieces of coral. At that time I wrote another thread about the treatment options: < http://www.bareefers.org/home/node/12988 >
A number of monti frags and larger colonies were lost completely, but other montis were untouched. I really didn't have the resources to deal with this infestation - no place to remove all the corals while treating them, and no time to do it. So, I decided to just see what would happen.
In April-June the tank was looking mostly fine. The acroporas were growing like crazy with great color, and while some Montis were definitely taking a beating, others were untouched by the nudibranchs.
Then in mid-June, a new pest started to crop up: asterina sea stars. Their numbers grew seemingly exponentially from a few to thousands. A green eyed chalice that I grew from about the size of a quarter to about 4" across was eaten from the rim to the center in just a week or so. I have two pieces of this chalice, and both were eaten. Other chalices in the tank were untouched. A big monti cap that had been getting slowly chewed by the nudibranchs all of a sudden had large totally dead spots at the edges. In both cases, there were tons of tiny asterinas at the edges of the "eaten" areas. I didn't look at the asterina gut contents, and while it's possible that they were just grazing on already dead corals, their population explosion coupled with the sudden coral loss was strong correlative evidence that the stars may have been eating the corals.
Again, I lacked the resources to deal with the sea stars as I was leaving for a 1-month series of trips overseas. I left the tank in the capable hands of my graduate students with the hopes of returning in August to deal with the nudibranch and sea star issues. I told them to just do regular (daily) small water changes on the tank and prayed for the best.
While gone my students wrote to me to let me know that the corals were looking bad. I asked them to check the pH, which they did, and it was about 7.5. Apparently, something went wrong with either the Ca reactor, the refugium, or their mixing of new seawater. I instructed them to raise the pH, which they did to some extent, but when I returned in August, many of the corals, especially certain acropora frags, had perished.
Also while gone one of the Tunze 7095 controllers stopped working properly. So, now the 4 pumps it controlled are just full on all the time. There's still a lot of flow in the tank, but I liked the flow pattern better before. I'm going to have to diagnose the problem - probably one pump that isn't working properly. Might be a good time to take them all out and clean them.
I did a whole series of water tests (pH was low, Ca and Alk were low, Mg was too high, salinity too high, PO4 was present), and started to aggressively correct water chemistry through water changes, new GFO media, new carbon, and addition of aquavitro products (which I don't normally use due to costs). The water chemistry is back to normal, and, hopefully the corals will recover. Some, like my Hawkins blue echinata that was growing well with great color, has died at the tips but is still alive at the base. We'll see how it goes. A rather large (4" across) tabling acro that was doing very well has died on top, but is alive on the bottom. I'm trying to not be sad about the corals I lost...
To deal with the pests: I have purchased a pair of harlequin shrimp in the hopes that they'll eat some sea stars. I'm looking for a dorid nudibranch that likes to track down and eat aeolids (the monti nudis are aeolids), but haven't found one so far.
It was also time for new lightbulbs and so I decided to put the 10K MHs on the tank in the hopes that switching from 20K would provide additional PAR and help the corals increase their photosynthesis rate. I reduced the photoperiod to 3h and increased by 30min each day (15 min earlier and 15min later) to an eventual photoperiod of 6h (10AM-4PM). I'm going to add the 2 reefbrite blue strips and have them on from 9AM-5PM or so. Might build a new canopy first, though, as the one I presently have isn't too pretty.
Finally, some of the corals have started stinging each other, so it's time for some fragging and DBTC. I need to set up a tank to QT frags before DBTC - I'll do povidone and potassium permanganate dipping with the hopes of getting the pests off before they go to other people's tanks.
It's tough to have a hobby tank also be a public display!
I'll try to post some pics soon.