Sea Water PH & Salinity

[eseow]

A question for some experienced saltwater tank keepers. What is the recommended specific gravity for a saltwater tanks & what should the ph be? I just pulled some sea water on high tide (incomming current off the coast inlet, right at the at the sea). Its measuring 1.018 to 1.019 SG, and 7.8-8.0 ph. Now, from what I was reading, marine books say ph 8.2 to 8.4 ph, and 1.020 to 1.024 SG for marine tanks. It not watered down from any rain. Hadn't had rain for a few weeks here in Miami. When I tested saltwater from wholesaler, it measured the same. They use natural sea water, and it appears so from my readings. Anybody have any comments on the subject, please post. ???
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[dattack]

I keep mine at 1.026.

*  35 PPT            1.0251            * Typical Ocean Value *

http://www.reefcentral.com/library/faq/reefkeepers_1.htm

Specific gravity changes with temperature.

[eseow]

I took original SG readings @ 75 Deg F. Thanks for the site post "Dattack"

[colesea]

Average offshore oceanic salinities are what dattack said. Coastal waters can be influenced by anything from rain, to whatever watershed is seeping in there at the time, and if I remember, a whole lot of Florida simply pumps it's wastewater into the channels and inlets around there. So if all of Miami flushed their toliets, you might have fresher water at your inlet<G>. Tides are wonderfully strange things. On a high tide with no wind or large wave action to provide the mixing, at a freshwater inlet you'll find that the salt water enters -under- the fresh water because it is more dense, creating a salt wedge along the bottom that can travel pretty far up the freshwater river without changing the salinity of the surface waters.  If you sample the bottom of the inlet you will find higher salinities than if you just sampled off the surface water.

For fish only systems I keep my salinities at 22ppt (SG 1.016 @ 76oF) simply because having lower salinities does reduce the amount of parasties and disease. Medically I've had the salinities as low as 15ppt (SG ~1.010 @ 76oF). If you plan to have inverts your salinities should be higher, probably around 30ppt.

There really isn't any set rule as to what the salinity ought to be in a marine tank. Most books simply recommened average oceanic conditions because, well, that's an average oceanic condition. Average doesn't mean that local conditions will meet these values at all times. What you need to do is keep your tank stable at whatever conditions you choose as appropriate for your fish. Personally, I would match my tank to the values of the LFS where you plan to purchase the majority of your fish from because that would make acclimation easier on your fish.
~~Colesea

[eseow]

My current tank is has only 4 fish, 2 crabs, & 2 snails. I was told to keep the SG @ 1.018 to 1.020 for now to keep parasites from thriving. This tank is still new, 10 days old. Keeping eye water conditions. I'm keepin it a 1.019 SG @ 76 deg F. So far, so good. ley*

[colesea]

Keep us updated, I'm quite curious how things go.

Good luck
~~Colesea

[eseow]

As for SG, I'm using two SG meters now. One is a plastic unit, with scale of SG. The other is a glass floating type with temp scale on it. Both read slightly different. Glass floater is reading about 1.024-1.026. This was @ 80 Deg F surf temperature, 1:10 am 5/2/02 high tide water at Newport pier (By Haulover pier area-using NOAA Marine Forecast Tide Prediction Chart for High/Low tide times in Miami Area). Its very warm down here now. Plastic SG unit still showing 1.018-1.019 SG reading @ same temp. Will test water @ 75 deg when I get home with sea water. I probably have a cheap plastic SG meter. Will post more results later. Oh, by the way, one Blue Devil Damsel has tail fin tearing and body sliming. Was told its probably due to fighting with other Damsel in the tank. All the other fish are fine. Water still reading OK. Placed hurt Damsel in breeder net to separate territorial fighting for now. He doesn't look like hes going to make it though.  miley*

[colesea]

Temperature can definately affect salinity, at least at the surface. I don't know which SG meter would be more accurate, I personally like the SeaTest Hydrometer because I'm used to reading everything in salinities (ppt). Specific gravity is slightly more accurate, but nothing about science is ever exact<G>. I can't remember a time I've ever used specific gravity during oceanography unless we were talking about sea water densities.  Of course more dense water will have higher SG because there are more dissolved substances in it<G>. Doesn't necessarily mean that dissoved stuff is salts. High particulate matter and dissolved solids will also read as high SG. Higher temps might give you higher SG readings as surface water is evaporated, concentrating your salinity and causing the surface water to get saltier and sink. This is without large wave action mixing.

If you want to check what the degree of deviation is between your two meters, get yourself some RO water from the store. The SG and Salinity of the RO water should read zero at standard temp of 23oC (or any temperature actually, you can measure at room temp if you'd like). If it does not, whatever value it is off is your deviation, and you'll have to subtract that many units from your actual readings.  It will also tell you how much deviation is between the two meteres as well.

Sorry to hear about the damsel. Poor guy. I don't have much luck with them either. I'll get a dozen in, and they'll kill each other off until only about three or four have taken up truce in the tank.
~~Colesea

[eseow]

Funny thing, started with 4 damsels, have 3 free in tank, none are fighting now. Only sick one in net & other blue damsel taunt each other every now & then between net. Other strip damsels have settled in. Burrowed tunnel in live sand under live rocks and stay there at night. I can't even find them in the morning. They come out of no where when food is present. Also, test sea water for phosphates, 0.1 PPM reading. Will test for calcium content next. This water has been filtered for 24 hours with filter floss & carbon with air stone box filter before testing.  ey*

[colesea]

Sounds like fun.

Damsels are cool fish. Sergant Majors are know for attacking divers to keep them away from nests and out of their territory<G>
Good luck.

~~Colesea