beachy Posted July 1, 2006 Report Share Posted July 1, 2006 I went to Takapuna today to get some nsw, this is the second time ive tried nsw, first time i went to Murawai. I have a swing arm type hydrometer, and when i mix up asw, i mix it to about 1.024. I have tested Takapuna water today and it reads 1.021 , as i understand its usually around 1.028. So if takapuna water is 1.028 today, my swing arm type hydrometer is way off, which i understand is not uncommon. So my next question is, should i put the NSW straight in, even though it reads 1.021, im a bit worried about lowering s.g to fast. I was thinking about buying a floating type hydrometer, are they any better than swing arm? I would love to get a refractometer but dont have the funds at the mo. Thanks in advance Quote Link to comment Share on other sites More sharing options...
raeh1 Posted July 1, 2006 Report Share Posted July 1, 2006 I don't even check my nsw anymore. Just goes in. maybe because of its temperature, the salt levels read differently. I would just bang it in... just me though Quote Link to comment Share on other sites More sharing options...
lduncan Posted July 1, 2006 Report Share Posted July 1, 2006 I have tested Takapuna water today and it reads 1.021 , as i understand its usually around 1.028. So if takapuna water is 1.028 today, my swing arm type hydrometer is way off, which i understand is not uncommon. Yes the fact that they're crap, combined with the fact that hydrometers are calibrated at a set temperature, 25 C will produce a reading which is way off, especially when the temperature is different from it's calibration temperature. However if the water is colder than 25 C I would expect that the hydrometer would read higher salinity as it would be more dense? The refractometers worth buying have automatic temperature compensation (ATC), which adjusts for temperature. Quote Link to comment Share on other sites More sharing options...
cookie extreme Posted July 1, 2006 Report Share Posted July 1, 2006 your hydrometer must be way off. i also got some water today from takapuna at 11.20 this morning (damn it was cold), what time did you go? guess i must have missed you by minutes (got htere just after high tide). well it showed 1.028 on my refractometer which seems normal for takapuna water. refractometer don't cost that much more then other divises but seem to give a more "accurate" reading. Quote Link to comment Share on other sites More sharing options...
beachy Posted July 1, 2006 Author Report Share Posted July 1, 2006 I was there at 11.00, and yes it was freezing , i was thinking i might see someone down there . I suppose its not safe to assume that 1.021 would mean 1.028 on my hydro? and then maybe aim for 1.019, just until i get a refractometer. My S.g must be around 1.031 at the mo Quote Link to comment Share on other sites More sharing options...
suphew Posted July 1, 2006 Report Share Posted July 1, 2006 I suppose its not safe to assume that 1.021 would mean 1.028 on my hydro? No because you have to adjust the temp to be the same as your refference, even a couple of degrees seems to make a difference Quote Link to comment Share on other sites More sharing options...
beachy Posted July 1, 2006 Author Report Share Posted July 1, 2006 Went to hollywood tonite, they tested my tank water with a refractometer, 1.032 my hydrometer was saying 1.023-1.024. Then tested Taka sea water 1.028 my hydro was saying 1.020-1.021. They recommended a red sea swing arm type, as i cant afford a refract at the mo, tested my tank water 1.026 :roll: so i guess its a closer read but still not close enough. I think i will aim for about 1.021 hopefully it will be about rite. Quote Link to comment Share on other sites More sharing options...
raeh1 Posted July 1, 2006 Report Share Posted July 1, 2006 I know how cold the water is at the moment.. Surfed raglan for 2.5 hrs on thursday.. Before collecting my water.. Got booties, titanium wetsuit, and surfers cap.. and still sssssssoooooooo cold... :lol: :lol: Two years ago surfed 4hrs midwinter thats really cold... (oh yeah my point is) the surf web sight says its 15.3 degrees in the water... I will check it out next time.. maybe even lower Quote Link to comment Share on other sites More sharing options...
wasp Posted July 3, 2006 Report Share Posted July 3, 2006 Yes the fact that they're crap, combined with the fact that hydrometers are calibrated at a set temperature, 25 C will produce a reading which is way off, especially when the temperature is different from it's calibration temperature. In fact most swing arms do not need temperature compensation as long as they are the same temperature as the water being tested. Unlike floating hydrometers which do need temperature compensation, strange as that may seem. Also do not assume your floating hydrometer is calibrated at 25 degrees. Many floating hydrometers are calibrated at 15 degrees. But it is correct that swing arms are not good, in fact IMO they should not even be sold. However as a short term measure Beachy you could assume that your water was 1.028 as per Cookie Extreme, so just know that when you're swing arm says 1.021, it's really 1.028. Even this can change over time though, my own swing arm I used to have would gradually change over time. Quote Link to comment Share on other sites More sharing options...
lduncan Posted July 3, 2006 Report Share Posted July 3, 2006 If swing arms compensate for temperature, they must use some plastics with interesting thermal properties. How does that work? Quote Link to comment Share on other sites More sharing options...
wasp Posted July 3, 2006 Report Share Posted July 3, 2006 If swing arms compensate for temperature, they must use some plastics with interesting thermal properties. How does that work? Kinda sound like you are doubting me again Layton. :lol: Check this Quote - "Swing Arm hydrometers (Figure 1). These types of hydrometers need no temperature correction, both by their own claim, and by some limited testing that I reported in a previous article. Whether accurate or not, the salinity values determined with such a hydrometer are fairly independent of temperature." I can elucidate further if you still don't understand. Quote Link to comment Share on other sites More sharing options...
Fay Posted July 3, 2006 Report Share Posted July 3, 2006 thinking about buying a floating type hydrometer, are they any better than swing arm? NO I have used both and for years over salted my tanks until I got a refractometer soon found out the correct readings. Always use to have to add salt mix after a NSW change because the two first ones were not reading correct have not had to add salt since I got the refractometer a few years ago. Quote Link to comment Share on other sites More sharing options...
wasp Posted July 3, 2006 Report Share Posted July 3, 2006 Good advice I tend to rebel against expensive / high tech, but in this case, a refractometer is the way to go. Not that expensive either. Quote Link to comment Share on other sites More sharing options...
chimera Posted July 3, 2006 Report Share Posted July 3, 2006 a refractometer is the way to go. Not that expensive either exactly, you can get reasonably decent ones for around $100 now. not a great cost to ensure salinity it right at every water change, especially considering too low/too high salinity is a quick way to kill corals (not to mention inverts and fish) protect your investment and splash out on a refractometer, or at least borrow one for starters. Quote Link to comment Share on other sites More sharing options...
0pius Posted July 4, 2006 Report Share Posted July 4, 2006 What about the digital salinity readers I have purchased one of trademe and I seem to be calibrating it alot which can get annoying, are refractometers better than there digital counter parts Quote Link to comment Share on other sites More sharing options...
chimera Posted July 4, 2006 Report Share Posted July 4, 2006 dont know, but dont need to calibrate the refractometer (depending on the type you get) Quote Link to comment Share on other sites More sharing options...
fishboi Posted July 4, 2006 Report Share Posted July 4, 2006 i am not a salty but saw this on trade me which i thought would be helpful http://www.trademe.co.nz/Home-living/Pe ... 153953.htm Quote Link to comment Share on other sites More sharing options...
beachy Posted July 4, 2006 Author Report Share Posted July 4, 2006 I will definately be getting one, b/days comming up soon Quote Link to comment Share on other sites More sharing options...
wasp Posted July 4, 2006 Report Share Posted July 4, 2006 You're onto it Fishboi Quote Link to comment Share on other sites More sharing options...
suphew Posted July 4, 2006 Report Share Posted July 4, 2006 dont know, but dont need to calibrate the refractometer (depending on the type you get) My refractometer has a small screw on the top, and should be adjusted every now and again, Its easy to do just need RO water and zero it in. Quote Link to comment Share on other sites More sharing options...
lduncan Posted July 4, 2006 Report Share Posted July 4, 2006 What about the digital salinity readers I have purchased one of trademe and I seem to be calibrating it alot which can get annoying, are refractometers better than there digital counter parts A refractometer is a better option. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.