This page contains all the tank events from 1 January 2008 to 31 March 2008.
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We had noticed that one half of the Finger Leather Coral seemed to be doing better than the other: lighter in colour, more open hands. On closer inspection, it has actually split into two.
The urchin was active yesterday and had dislodged a rock from the top of the wall in the tank. The falling rock must have hit the Blue Linckia and severed one of its arms while slightly damaging another. We will have to see how it fares.
Time for an update on our Fragging attempt. A few lessons:
So, since our quite attractive razor shell base had a flaky surface and wasn't sufficiently stable (hence fell over and the frags were eaten by the urchin), the fragging was not a huge success. That said, the Gorgonian is not particularly bothered by being partially eaten and we still have the two large halves (which we have reattached to rocks in the tank now). For our next attempt at fragging we're going to remove the frags to the sump tank.
The Bangaii Cardinal didn't come out at feeding time today. No sign of it in the tank or the sump, so likely it pegged-it and has been efficiently cleared away.
Some of the corals are now beginning to suffer in our zero water-change experiment. Here are some "now and then" pictures so that you can see the difference.
The other corals (Green Fungia, Euphyllia, Gorgonian and Red Sea Pulse Coral, Euphyllia "hammers" and pair of mushroom polyps) and the fish don't seem to have been affected.
Checking the vital statistics in the tank:
The redox level has also been steadily reducing since Christmas:
The pH is steady at just over 8.0 and the salinity is steady at 1.210.
From this data it looks as though a water change roughly once a month would be about right to refresh the magnesium and compensate for the deficiencies in filtration. Not entirely sure my little reservoir of coral sand is making any difference. Time for a water change...
We've been watching the redox graphs on our live data page and it seems pretty consistent that on a water change the redox drops dramatically. The graph below shows the drop occurring; the water change is just 10% (30 litres).
We've heard suggestions that if the aquarium is sufficiently filtered and is not heavily loaded then water changes can be vastly reduced. These sudden drops in redox can't be good for the fish, so after a water change at the start of December last year we decided to halt them and see what happens. A month on and nitrate levels remain stable (around 15 mg/l) while average redox levels are way up at 340 mV. However, we have noticed that the coraline algae is starting to die back. See the white patches developing on it below.
It seems likely that it is missing the nutrients in the salt that forms part of the water change. Also, redox has an inverse relationship with pH, so while our redox is high the pH has dropped to just under 8. In an attempt to add nutrients and increase the pH, we've rigged-up a small reservoir in the flow of the top-up system. It consists of a small plastic container (10 cm on a side) with a hole in the bottom just big enough to snugly fit a piece of 5 mm plastic tubing. The top of the tubing is just below the top of the container and the container is then half filled with Aragonite Coral Sand. The top-up water flows through the sand and the hope is that it will the gain some buffering potential and nutrients along the way.
We'll see if it does any good.
On other matters, we're down to one Cleaner Shrimp again: don't know which one died or when it went. Also, the colony of Zoanthids we bought a couple of months ago isn't doing at all well. We've tried moving it but nothing seems to make it open up.
And finally, for the record, here's an overall view of the main tank.