Xenia crashed

[dgibbs]

I have a 75 gall tank with a 20 gall sump.The lights are two 175 watt 10000k mh.
I did a 10 gall water change using instant ocean{sg 1.025 temp 82 degrees}.The water was mixed for 24 hrs.I have been doing this once a week for the last month to get nitrates down.I have been using water from a recharged TWP.The resins were well rinsed after the recharge.I have been using the same water for previous water changes with no ill effects.Almost as soon as i completed the water change my green star polyps,colt,and pulsing xenia closed up.This morning everything looked okay exept the xenia.It is shriveled up and turned a kind of purple.Before the water change it was plump, fully extended and pulsing like crazy.I looked in the sump/refugium with a magnifying glass and mysid,amphipods,plankton etc,look okay.The xenia are in five colonies in different areas of the tank all look the same.There was no significant ph swing after the water change.
ph 8.0-8.5
Ammonia 0
Nitrites 0
Nitrates 5 ppm
Phosphates 0.2
KH 9
calcium 375
Any thoughts on this would be appreciated, thanks.

[Edited by dgibbs on 01-21-2001 at 12:33 PM]

[rshimek]

Hi,

Well, I like the concept of every effect having a cause. It definitely seems as if something in the water was the culprit. Are you sure there was no pH shift? I have had two instances of my Xenia "instantaneously" dying and in both cases I was able to trace it a high pH spike (caused in both cases by my kalkwasser drip turning to a kalkwasser flood). In both of these cases most everything else in the tank weathered the storm without long-term harm.

If it wasn't pH, then I suspect it was something else in the water, but trying to diagnose it a posteriori from this distance may be fruitless.

What do you think the cause was?

[dgibbs]

I just tested the water from the TWP with my pinpoint monitor.The ph was 11.21
I added IO,the ph was 9.28.I then did the same with RO water from the LFS.The ph was 8.84 without salt and 8.20 with.
When i did the 10 gall water change maybe it could have caused a temporary ph swing at the top of the tank.
The two chemicals used in recharging the TWP are hydrochloric acid and sodium hydroxide.Maybe there is some residue left in the resin.

[rshimek]

Hi,

I would bet that there was some chemical residue. I think anything approaching a pH of 9 would fry the Xenia. If your water made up from TWP water and IO really has a pH of 9.28, that is far too to add rapidly and in quantity.