Sorry for the late reply - things got away from me today.
Thanks for taking the time to give such a thorough reply !
It's my pleasure to help. I've been keeping SPS since 2006, so if it can happen, it's probably happened to me! (Aquarium-related and non-aquarium related LOL)
So generally I test alk once a week and this week was a fairly large swing compared to average down to 7.3 from 7.7, but over the course of a week maybe not too drastic?
No, doesn't seem drastic. I prefer to test Alk minimum twice a week. I test daily on my SPS tank, when I'm changing the dosing volume on Alkalinity, or for PO4 if I'm low and trying to raise/stabilize.
Po4 is fairly steady at 0.4 to 0.5 despite my attempts to lower it with lanthanum. I have changed make of lanthanum in recent days if that could possibly be a cause. (Tested again today and still 0.47 so no drastic change)
Got it - the numbers aren't worrisome to me (Anything above 0.03 ppm I'd call 'OK'). But let me say this; ANY (and I mean ANY) time I have an issue with Dinos it's because I let my PO4 bottom out. I can count on it like taxes man. 0.02 or less on the Hanna checker means Dinos are showing up in less than 36 hours. While this may not be true for every scenario, raising PO4 is FIRST thing I do when they show up. Once I have PO4 ~ 0.10 ppm, the Dinos are gone within a week. This is also pretty standard in most Dino treatment protocols. So, I'm curious why trying to lower PO4 w/ the Lanthanum Chloride? If you don't have a specific algae issue you are trying to remedy, I'd stop (and even if I did, I'd take the algae any day over the Dinos). Consider pausing the LC dosing.
The bonsai has been base to base with this for at least a year and no noticeable death where they actually touch.
Oh wow. Almost as certainly as I can count on Dinos showing up after a low PO4 reading, I can count on allelopathy between corals - even if it's not 'obvious'. Let me illustrate: So I recently acquired a 2-branch fragment of a PC Rainbow from my brother. I always remove the old plug and transfer the frag to a new one (for many reasons). When I did this, I managed to break the frag in half. No problem - I just epoxied both branches of the coral right next to each other on the rock. After a couple weeks I noticed the part of both branch bases were bleached dying, but chalked it up to the corals just adjusting. My brother came over one day and noticed this too, except he could see the corals' Mesenterial filaments extended between each other. He's like "hey man - you need to move these corals - they are trying to kill each other". He was floored when I told him they were to frags of the exact same coral that he a given me a couple weeks prior.
The anacropora is a more recent addition (within the last month) so there is potential there for a reason ?
I'm not a marine biologist, but it would seem logical that there is potential for additional/increased allelopathy if one coral is sensitive to another. While you may not 'see' them 'fighting' - the new anacropora could definitely be raising the defenses of either neighboring coral.
I think the bare spot under the bonsai is from lack of light as it is completely shaded .
Makes sense.
I am currently struggling with Dino's in the tank, not sure if that is what's on the coral there or if that's just shaded also I will investigate that !
See my note above on PO4/Dinos.
so flow could definitely be a cause of the issue now I think about it. There is an mp40 top left you can just see. It's placed above and in front of the rock with the acros on. Flow probably struggles to get from the other side also because of the shape of the rock.
I saw this, and agree on all aspects.
'll probably add something extra to get some flow towards the bases of the acros.
Yes, an additional powerhead will almost certainly help. A powerhead moving water along the back side of the tank I think would be a huge help. While it may seem odd to some/most, I'm a firm believer that water movement trumps even lighting as the #1 aspect of SPS-keeping. If I needed to make a decision on the root cause, I'd call it a combination of lack of good flow AND allelopathy, leading to the necrosis, and would take immediate steps to remedy (the former will be much easier than the latter).
I've just put the 2 blades on top of the tank which aren't connected yet so will have some extra lighting on those areas too.
Ah that's great - will help with providing better 'blanket' coverage/shade-reduction. Get those puppies running !
Can the necrosis spread from lack of flow like regular stn or will it remain localised to the area which isn't getting the flow ?
I've seen it both ways. Any tissue necrosis increases the chances for a bacterial infection (in most all organisms). However, when I have had flow-related problems with corals - almost every time I can remember - when I fixed the flow, the coral began to heal. You're already doing a good job of tracking it, so just continue doing what you are doing. If the coral tissue starts to recede again, and it looks like it may not stop, I'd consider the fragging the coral up to try to save it. Until then, I'd put my money on the coral recovering assuming everything else is back in line.
Doesn't seem to be much change today and haven't done anything as yet
That's great.
If it were me, I'd add a powerhead ASAP, and get those lights running. Consider moving the anacropora a little further away than it is now. Not much you can do about the coral bases touching. If add the flow and lights, and shift placement of the anacropora and things still continue to degrade, I'd consider relocating one of the two colonies. (Or, you may be forced to whether you want to or not).
Let me know if there is anything I'm saying that doesn't make sense. I think the odds are in your favor, as you have caught the issue before anything major has happened, and you seem like a capable hobbyist.
Beautiful tank by the way! Will be following for updates...
