Specific Gravity Of Your Marine Tank

[steelhealr]

Sometimes it's a good idea just to keep old topics fresh. Anyone who hits the search button will always be able to get some good information. Feel free to comment. SH

 

[Fish Fingers]

My S.G is 1.027, the same S.G at the great barrier reef where my corals come from. That wasn't an option though so I couldn't vote for it .

 

[Mr Miagi]

Im 1.026, but i think the Poll might be better off without say 1.021 and 1.022 and have higher SG's like 1.027 and 1.028.

I use a floating hydrometer at the moment. Sub-standard i know...

I tend to measure SG every other day. I frequently watch my tank, so why not check basic params whilst im there!

 

[steelhealr]

This is the first I"ve seen/read people keeping their tanks s.g.s at greater than 1.026. From my reading, I try not to exceed this as I've read SOME info on it putting stress on some fish's excretory systems. SH

 

[crazyelece]

Fish like 1.020 corals like 1.027 so most people have both and have to compromise thus getting the 1.024 and 1.025 as the most common goal. I keep both my FOWLR tanks at 1.021 and my new nano reef at 1.025 measured with a refractometer. My brother, who was using a swing arm hydrometer, thought he was doing the same but when I measured with my refractometer his box was off by 0.003. Most swing arms are consistant you just need to get them calibrated so you know how far off it is.

 

[Fish Fingers]

This is the first I"ve seen/read people keeping their tanks s.g.s at greater than 1.026. From my reading, I try not to exceed this as I've read SOME info on it putting stress on some fish's excretory systems. SH

That may be true SH, I'm nto sure. I just like to keep my stock in the closet parameters I can get to their natural environment. From what I've read its better to keep your tank's S.G at 1.027-1.029 than from 1.020-1.022.

 

[steelhealr]

I'd be interested in seeing any links on the s.g. 'down under'. Most research I've done suggests the oceans average s.g. away from runoff areas to be 1.026. I checked the s.g in L.I. Sound, and it was low..1.021-.22...but..probably all runoff. SH

 

[Chac]

Most research I've done suggests the oceans average s.g. away from runoff areas to be 1.026.

From what I have read/heard you are correct SH & that most peeps keep there tanks around this mark

 

[Navarre]

1.027-1.029 is very very high. From my research and fellow hobbiests that study the great barrier reef, the specific gravity is closer to 1.024-1.025. Of course, where there are shallow laggons and little exchange of water to the open sea then you can expect the SG to be higher. The Red sea is known by many to be a higher SG than most other reefs in the world. The Red sea has an SG of 1.026

I keep mine at the same sg as the sea around me. 1.025

 

[Donya]

looks like I'm the only daily checker lol. I guess it would have be be checked less frequently on larger tanks where evap doesn't have such a big effect. Mine is at 1.023 right now.

 

[steelhealr]

I"m happy Navarre weighed in on this. I truly respect his opinions. I believe that for most of us a s.g. of greater than 1.026 can place stress on the fishes excretory system. The animal must concentrate it's waste to a high degree against a very high osmolar gradient. Hence, one of the reasons that SW fish do not tolerate nitrates like FW fish do..nitrates concentrate to a much higher concentration and reach toxic levels much quicker than do with FW species. Unless you own a fish that typically lives in a higher s.g., eg, the Red Sea as Navarre has mentioned, I wouldn't exceed 1.026 for the most part. SH

 

[Fish Fingers]

Thanks for your input Navarre. I got this info from a very respectable and knowledgable person on the australian fish forums, so I'm not going to go either way. I know for a fact that the GBR has a S.G of 1.027, as he and my cousins have both tested it there numerous times. My NSW also has a salinity of 1.027. I'll go and see if I can find some quotes on it from the forums, though I doubt I'll find anything. Maybe maigi will be able to help me out?

EDIT: Found some info about S.G on his website, I think he reccomends a S.G of 1.025-1.027, although its too much reading for me to find out exactly . I'll keep looking for my some evidence on my 1.028-1.030 statement, maybe I just made it up???

Website: http/www.petsforum.com/personal/trevor-j...ficgravity.html

EDIT 2: After a bit of searching it seems that most aussies keep their tanks at around 1.027 and 1.028 whereas americans keep theirs lower (there was a thread on this subject). Hope this helps!

 

[Navarre]

Just out of interest, do you test SG with a hydrometer or some other device.

I use natural sea water in my reef system. Straight out of hte ocean and directly into my tank within 2 hours (sooner if possible).
The SG along the cornish coast in the UK is 1.025 and this is tested with a refractometer.



I had a terrible disaster in my old 100 gallon system with SG. I went a long time monitoring it with a Hydrometer and got a reading of 1.024. When i got my refractometer the true reading was actually 1.030 !! I had only placed an achilles tang in this system the day before. Within 4 days of its arrival it was dead and a mere husk of what it was. It turned from a very fat healthy ish into a skeleton. Now i know Achilles are very very delicate fish but the only reason i can see for its quick demise is the high SG (And the red sea is considered high SG). The SG was so high that it completly dehydrated the fish from what i can tell.
I then had to slowly reduce the SG of the system over a period of 1 month to get levels back to normal. The amount of stress that high sg places on a fish is very high indeed. I also see a good argument for running low sg so that parasites find it harder to acclimatise in systems.

 

[Donya]

How does one calibrate a swing arm or other type of hydrometer? In the absence of access to a refractometer, would a known solution with a known sg at a measured temperature work to calibrate?

 

[RoyalGrammaPrincessHannah]

Well I need a refractometer. The swing arms are crap. I have a deep-six, then I got an Instant Ocean one free from someone who gave me a bunch of stuff from his old tank. They are about .002 off from eachother. So right there, that proves something.

Anyway, I know I want my SG at 1.025 [which is what I supposedly keep it at now] and I know that salinity is measured in ppm, but how many ppm do you want?