Can't keep SPS alive

[Delphinus]

Is there any truth to the saying that you can't mix SPS and LPS?
Maybe the LPS are releasing something into the water and its killing the SPS??

I don't think so.. LPS are SPS are really very similar to one another except in terms of scale. Usually what is good for one is good for another, although I think LPS may be more tolerant of lower light levels and usually require less current that SPS. AFAIK, the only times you really ever run into trouble with LPS and SPS not getting along is when one is stinging the other (it's a more direct form of warfare), which is usually the same problem you get with SPS vs. SPS.

And it's not always LPS that wins, either. I've had a hydnophora (SPS) take out a few heads of candy cane (LPS) -- luckily the candy cane seems to be a quick grower.

Now, with that said, ....

There is wishy washy talk of some softies (leathers I think) secreting compounds that inhibit/slow growth with sps, but carbon removes this. Are you running carbon?

I'm not so sure it's all that wishy washy... I think there are genuine issues of compatibility between softies and stoneys... Leathers can supposedly secrete compounds but I'm thinking even in terms of just things like mushrooms and octocorals. A mixed reef can be very hard to manage, and that's one reason (IMO) why usually you see someone unload their softeys (or make a new tank) when they try to get real serious about SPS. Allelopathy, aggressiveness, invisible compounds, ... There could be something to this. Apparently even the presence of caulerpa in the tank system can have an effect on the growth of SPS due to allelopathy. For sure, running carbon is not a bad idea.

...

What sticks out to me though is the Ca and Alk values. They seem "not bad" but I think they might not be all that optimal either. Ca seems a hair on the low side, and your Alk seems to be a little jumpy... For Ca, I think NSW is more like 380 or something like that. I like to aim for >400 myself for Ca, and 4.0 meq/L for Alk which is .. um .. 11dKH (if I remember my conversions correctly). If I do remember my conversions correctly, your Alk is going from 2.4 meq/L to about 3.8 meq/L. I think anytime you're under 3.0meq/L you can expect to see very minimal growth in your stoneys. They say NSW is something like 2.7 meq/L, that means to see growth equivalent to the ocean your levels should never drop below 2.7.

Good luck. Getting into SPS can be a bit of a learning curve. Don't get discouraged!!