Safe to do water change using saltwater mixed over a month ago?

[fullerenedream]

Please be gentle: our reef tank's primary caregiver is experiencing an extended illness, plus our family is fairly new to the hobby.

We mixed up a bucket (one of those big Rubbermaid buckets) of RO water and Red Sea salt at least a month ago, intending to do a water change. Life (and illness) happened, and we haven't done the water change yet.

The mixed water has been sitting in the bucket all this time, with the lid halfway off, dust and cat hair floating in, and presumably microbes breeding in the water. I just checked the salinity of the bucket water and it's at 40 ppt, so I guess not the *perfect* breeding ground for microbes, but not too salty for stuff to grow in.

I scooped a bunch of cat hair and dust off the surface of the water. I'm guessing whatever hair and dust are left in the water are probably not worth worrying about (please correct me if I'm wrong).

Here's my question: once we adjust the salinity to 35 ppt, is it safe to use this mixed-over-a-month-ago standing water for a water change? Or would the microbes in it be too much of a concern?

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Tank Details:

tank volume: 123 L (32.5 gallons)
skimmer, filter floss, activated carbon, bioactive balls, Phosphate Minus phosphate remover

tank residents:
a green rhodactis mushroom coral (thriving)
a corynactis californica, aka "strawberry anemone" (thriving)
a zoa (seems to be mostly ok but not thriving)
3 LPS corals (struggling - I think from too much light&flow and too-infrequent feedings - we're trying to fix that now)
2 clownfish (thriving)
2 hermit crabs (seem fine)
1 flametail blenny (sometimes looks a little gray and gets stuck curled up sometimes, so I've been hand-feeding him a strip of sea veggies and a tiny-julienned pea every evening for a couple months now)
2 small and 1 big conch (seem happy)
3 turbo snails (seem good)
4 bumble bee snails (seem fine as far as I can tell)
2 nassarius snails (presumed alive - haven't seen them in a while)

1 sea hare just died (yesterday I think) and was removed this morning (so definitely time to do a water change)

various hitchhikers: lots of amphipods and spirorbid polychaete worms, some other feathery filter feeders, two kinds of sponge (one white, one blue), and some hydroid-looking things that don't appear to be doing any harm, tiny bit of bubble algae (doesn't seem to be taking over so far)

ongoing issues:
hair algae (better than it used to be, but let's just say there's still enough that I don't think the sea hare starved)
red planaria (I try to scoop some out with a net every day to keep the numbers down while we consider getting a scooter dragonet or one of the recommended wrasses or some other potential planaria eater)

Please be gentle: our reef tank's primary caregiver is experiencing an extended illness, plus our family is fairly new to the hobby.

[mcarroll]

11 hours ago, fullerenedream said:

I just checked the salinity of the bucket water and it's at 40 ppt, so I guess not the *perfect* breeding ground for microbes, but not too salty for stuff to grow in.

I scooped a bunch of cat hair and dust off the surface of the water. I'm guessing whatever hair and dust are left in the water are probably not worth worrying about (please correct me if I'm wrong).

Here's my question: once we adjust the salinity to 35 ppt, is it safe to use this mixed-over-a-month-ago standing water for a water change? Or would the microbes in it be too much of a concern?

40 ppt is pretty damn salty....enough to retard the growth of some microbes and bacteria.  (For what it's worth.)

 

Once you add back the evaporated H2O to get 35 ppt sea water, then it should be fine to use IMO.

[KC2020]

Tide pools in many areas of the world will often hit 40 ppt after a few hours of sun and wind. I've worked with The Nature Conservancy in measuring water quality along the California coast and in the tropics. Plenty of life, microbial in particular, endure this level of salinity on a daily basis.

 

If you have time, aerating the water in the Rubbermaid bucket for 24 hours will raise its pH and buffer the potential of lowering the tank's pH as a result of the water change. Keep an eye on the tank's skimmer after the water change if you're doing a large amount of water.

[mcarroll]

On 4/1/2024 at 7:41 PM, KC2020 said:

Tide pools in many areas of the world will often hit 40 ppt after a few hours of sun and wind. I've worked with The Nature Conservancy in measuring water quality along the California coast and in the tropics. Plenty of life, microbial in particular, endure this level of salinity on a daily basis.

Very cool!

 

It may be worth pointing out that tide pools also may reach freshwater levels of salinity (< 0.004 s.g.) during heavy rain events, which are fairly common and can be very large.

 

We have to realize that a few hours at elevated (or reduced) salinity levels can be normal – for a tide pool.  But even a tide pool doesn't stay that extreme for long – generally between tides, so a few hours.  

 

Continuous 24/7 hypersalinity, like a home reef tank might experience, is different.  But how different are actual hyper saline environments?  Apparently very, very different.

 

Salinity has a large impact on the makeup of microbial communities, generally speaking.  In journals, I've seen salinity called the #1 factor that determines the makeup of microbial communities.  

 

Lifeforms like all our reef critters and the associated microbes which are comfortable (adapted) at 1.025 s.g. are decidedly less comfortable at 1.030 s.g.  

 

For an example, my understanding is that ordinary nitrifying bacteria start choking out around that level (1.030 s.g.)....becuase of this, wastewater treatment (for example) is also VERY different under hyper saline conditions.  

 

We can see that elevated salinity is not inconsequential to our tanks and concerns.  

 

BTW, what is a tide pool?  A harsh place to live. 😉 But (maybe?) less harsh if you're a halophile.  

 

Also, what about reefs in the Red Sea?  The Red Sea has higher salinity (1.027-1.031 s.g.), but (like tide pools) it's also apparently much different than other tropical reefs.  

 

Note that range of salinities generally falls UNDER 1.030 s.g.  Also note that the Red Sea reefs there are better developed in areas of lower salinity. (These are coincidentally also areas with less extreme water temperatures.)