Salinity vs. Alkalinity, pH and Ca

[karimwassef]

I started wet skimming to address a dino problem, and topping off with RODI or Kalk water (depending on pH).

As the salinity dropped from 40 to 25 (SG of 1.030 to 1.019), I maintained my calcium and alkalinity as well as pH with kalk + 2 part + CaCl ... pH 8.4, dKH 8.5, Ca 460ppm. This took a week. I also maintained Mg above 1400.

Over this period, my coral polyps showed great expansion and color. In fact, at 1.019, they look better than they ever had.

But I was worried that this was getting too low, so I added salt to get up to 1.022 over 4 hours. They didn't like it. All scrunched up and unhappy.

Anecdotal evidence aside - is there harm in running low salinity if pH, Alk, Ca and Mg are maintained? I'm assuming running long term, I would need to dose other traces like Strontium and Molybdenum. Maybe Iodine (no Randy - I won't really go that far ). Fish food has the rest of the stuff?

I guess it comes down to Sodium salt vs. Calcium salt ?

 

[Randy Holmes-Farley]

Don't know if this is exactly what happened, but imagine the polyps as semipermeable membranes, like cells are.

Lowering the salinity outside will make them expand as water rushes in to equalize the ionic strength.

Raising salinity outside makes them shrink as water rushes out to equalize ionic strength.

If this is the case, higher polyp expansion is not a sign of health.

 

[karimwassef]

It wasn't a temporary expansion for hours. This went on for days with the corals actively expanding and contracting their polyps between day and night.

 

[Randy Holmes-Farley]

I still wouldn't assume it was going to be healthier (or even survive) in the low salinity water.

Maybe it is time for you to experiment.

 

[karimwassef]

So I went for a day and night at a salinity of 25 with positive results.

If we're talking controls, I am running in the 72-74F range and dosing H2O2 at 50ml a day in 600g (for reference).

What do you have in mind?

 

[Randy Holmes-Farley]

I just meant try to keep the same coral at low and normal salinity and see what happens over time.

 

[karimwassef]

That would require control tanks with reef capability... Out of my budget at this time.

 

[bertoni]

72-74 F is a rather low temperature range for a reef tank. I'd move that up to 80 F or so, if you have the more common animals. Is the low temperature part of the attempted cure for dinoflagellates?

 

[karimwassef]

I usually keep the tank cool 72-77 at most. High temps increase algae growth for me.

My halides auto shut at 80 and my I start to take equipment offline above that.

In the summer, my chiller and AC work to keep the 77, maybe a little drift to 78.

I never heard of running a reef at 80. This is my first reef since 2002 though. Back when I started in the 80s, it was about keeping it cool?

 

[bertoni]

This article goes into temperature ranges for a reef tank:

http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

The canonical average for a reef might be more like 82 F, but 72 is very low. If you're keeping species from cooler areas, though, it might be perfect. 78 F might be a good compromise if you're worried about overheating.

 

[karimwassef]

I'll look at raising it to mid-70s.

I see temperature as an accelerator. Good get better and bad gets much much much worse fast. It's a new reef and I've struggled with GHA, and now dinos as well that flatworms and now marine velvet.

It's like driving at 30mph... Instead of 70. It gives me more opportunities to fix things.

 

[Randy Holmes-Farley]

Maybe. It might also be stressful for organisms adapted to live at higher temps.

 

[karimwassef]

Ok. Back to my Ca vs Na question? Is there harm in an artificial system where salinity is lower if the reef elements are maintained (Ca, Alk, Mg, pH)? What is this harm?

 

[disc1]

Ok. Back to my Ca vs Na question? Is there harm in an artificial system where salinity is lower if the reef elements are maintained (Ca, Alk, Mg, pH)? What is this harm?

Osmolarity certainly comes to mind. It greatly affects the corals ability to uptake and get rid of any ions they need to move around.

 

[coralsnaked]

Not sure why the experiment?...But if you are trying to beat Dinos in this fashion you will probably fail. Lower Salinity and lower pH, as well as blackout periods and wet skimming and nutrient control in most cases doesn't work; and in the few cases where it seems to have worked is most likely the Dinos playing themselves out on their own,

IMHO and IME I have found the only solution is to stop nutrient exports and induce pest algae micro and macro as well as cyano bacteria, especially cyano bacteria to out compete the Dinos. Once the Dinos are gone then one can deal with the cyano and algaes with mainstream methods.

I believe and have seen Dinos be more prevalent in systems that are too pristine and algae free. Although fresh water will kill them it is not a beneficial method of removing them from the reef system as they are a type of zooxanthellae algae and therefore anything that will kill it will also kill corals, IE: fresh water dips with the exception of some soft corals such as zoas and palys. SPS cannot tolerate freshwater dips . In addition fresh water will also kill nitrifying and de-nitrifying bacteria in live rock.

 

[karimwassef]

On dinos - I'm almost out of that phase. This isn't a dino control method.

It's an accident that "seems" to have helped my coral expansion. This isn't just osmosis. For example: My LPS bubble coral went through its normal fill-flushing-tentacle modes as usual. The only difference is that the polyp expansion during the fill stage was exceptional. Same with my porites polyps and my rosetip bubble.

It's not just that the corals looked great. It's that I expected them to be dying at a salinity of 25... The difference between normal low salinity and my case is that I proactively maintained the "reef 4" - Alk, Ca, Mg, pH. All were kept optimal - and it looks like that was enough.

The hardest to keep up was Mg, but I did it.

 

[Randy Holmes-Farley]

I'm just not convinced that polyp expansion in low salinity is any indication of a positive effect.

Put an LPS is very low flow and it gets really big too. Is that better?

Growth rate over time would be a better indicator.

 

[karimwassef]

But shouldn't all my inverts including coral (soft and hard) be withering away at 25? Instead, they're feeding, expanding, etc...

I agree on growth but that'll take months

 

[disc1]

But shouldn't all my inverts including coral (soft and hard) be withering away at 25? Instead, they're feeding, expanding, etc...

I agree on growth but that'll take months

I think his point is that sometimes withering away looks like expanding and healthy depending on what is causing the withering.

 

[karimwassef]

Ok. I've let it come down to 27 = 1.020 (remember I had chickened out and raised it to 29 = 1.022). But I also raised the temp to 76 (still like taking things slow).

I'll take some pics today and you can tell me what you see.