Measuring the salt

[Amber]

What is the best way to measure the salt for a brackish tank, I mean the hydrometers are wired up for marine tanks and so the scale is way over the top for someone who wants just a slightly brackish set up like me.

Any tips?

 

[chris_1127]

i've been using a glass marine hydrometer for my brackish tank and not had too much trouble - the scale is fairly high in comparason but it is quite clear at the lower end still. i currently have the tank around 1.005 which is among the bottom 4th and 5th markings. but also when i do water changes i use the same volume of water, and know roughly how many dessertspoons of salt it takes to raise it to the correct SG.

If you are having trouble it may be worth looking in a brewing shop - you can get brewing hydrometers in all sorts of scales, they may do one with a much finer scale from 1.000 - 1.010

out of interest what sg are you trying to achieve?

 

[CFC]

Brewing hydrometers measure alcohol content not salt, one member before was using one and wondered why it took half a kilo of salt to bring the SG up to 1.005 in her fairly small tank

Most aquarium hydrometers will measure from 1.000 to 1.020 in 0.002 calibrations which is fine for brackish, remember conditions in brackish enviroments change all the time so the SG does not have to be as steady as it does in marine tanks.

 

[chris_1127]

) oops - i thought brewing hydrometers measured a liquids density (and therefore content of sugars or other dissolved solids) in relation to water? alcohol content is measured by the change in sg from the original liquid to the final fermented brew, and is usually calculated with a formula or conversion chart.. may well stand to be corrected here though...

 

[Pufferpunk]

Since you should only be raising the SG .002/weekly water change, I'd definately find one that starts at 0. Instant Ocean & SeaTest make hydrometers that start at 0. And you are measuring marine salt. Floating hydrometers are calibrated to measure liquid in the range of degrees somewhere in the 60s.

 

[Amber]

out of interest what sg are you trying to achieve?

About the same as yours Chris

 

[chris_1127]

glass marine one should be fine then, mine starts from 0.998 and the 0.002 increments are easy enough to read off

 

[Pufferpunk]

If you use the floating-type hydrometers, then you must adjust for temp, by using this: Salinity Calculator Seems line a PITA to me, since the fill-up type are <$12.

 

[chris_1127]

yeah but only the once if you are adding water at the same temp as the tankwater that you are testing...

 

[Pufferpunk]

HUH?

 

[chris_1127]

if you are raising sg at a constant temperature then the hydrometer reading will be the same and there is no need to use conversion factors. ie you know what temp your tank is at, you know the hydrometer reading for your desired SG at that temp, you have water to be added at the same temp as your tank and you bring the sg of that water to the same hydrometer reading.

 

[Pufferpunk]

You're still not making any sense. Let's say you are aiming for a low-end SG of 1.005. The reading on the floating-type glass hydrometer at a temp of 78 will be incorrect. You'd have no idea what the real SG is, unless you use the conversion chart. Otherwise it's totally guess work--not good.

 

[chris_1127]

its not really rocket science is it? im making the assumption that you also keep your tank water constant and do any water changes with water at tank temperature, therefore the correction factor is constant, and so once you know what reading you are aiming for, there is no need to recalculate. besides, if a hydrometer is calibrated for 25 degrees c and your tank is at 25.5 or 26, its a minute correction thats applied anyway - i think my hydrometer actually states what accuracy it can be relied upon to at within a degree either side of 25 degrees as well. the scale is linear too, so its not like you even have to use any complicated formulae to work it out.

 

[Pufferpunk]

How do you know the correction is linear? Why would you need the calculator then? It could just say, add so much for each degree of correction. Wouldn't it just be easier to spend the $10 or so dollars to have the right measurement? Actuallly, I use a refractometer.

 

[chris_1127]

in a word, physics the correction is linear relative to the calibration temperature of the hydrometer and the temp that you are measuring at, as both of these factors affect the readings. cant work out if your trying to make a valid point, or just being argumentative

my only point here really is that ive used a cheap-ish glass type hydrometer and have not had any problems using it or calibrating it. i havent used any other type of device for measuring sg, mainly because the glass one was the cheapest one that the shop could reccomend as accurate for the money i had to spend - what i do know though is that if i wanted a conductivity meter or refractometer for more accuracy it was gonna cost more than an extra tenner.