Hydrometer question

[hippyman]

I just started using a marineland InstantOcean hydrometer, but I'm not sure I'm using it right. I saw the woman at the LFS use it, to measure my test sample, which let me know my salt level was too high, but now, I cant get it down, even after all I did. The other night, I took out 5 gallons of salt water, and put in 5 gallons of fresh, now they said this should have fixed it, however, in my 75g tank, I'm still measuring too high of a salt content. Could I be using the hydrometer wrong, or could it be malfunctioning?

[Randy Holmes-Farley]

They can be inaccurate, but let's assume it is OK for now.

What is it reading? We may have a different opinion of what is too high. :D

[hippyman]

They can be inaccurate, but let's assume it is OK for now.

What is it reading? We may have a different opinion of what is too high. :D

I'm reading it at around 1.027, I was under the impression that it should be down between .024, and .025

[Randy Holmes-Farley]

IMO, it is fine where it is. Normal seawater at 35 ppt has a sg of 1.0264. You're within spitting distance of that, but again, the hydrometer may not be accurate.

Anyway, you might slowly drop it a little but, but there is no rush.

This has more:

The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 1: The Salt Water Itself
http://reefkeeping.com/issues/2007-03/rhf/index.php

from it:

http://reefkeeping.com/issues/2007-03/rhf/index.php#13

What Salinity to Use?
For reference, natural ocean water has an average salinity of about 35 ppt, corresponding to a specific gravity of about 1.0264 and a conductivity of 53 mS/cm. Salinity, however, does vary substantially from place to place.

As far as I know, little real evidence suggests that keeping a coral reef aquarium at anything other than natural salinity levels is preferable. It appears to be common practice to keep marine fish, and in many cases reef aquaria, at somewhat lower than natural salinity levels. This practice stems, at least in part, from the belief that fish are less stressed at reduced salinity. Substantial misunderstandings also arise among aquarists as to how specific gravity really relates to salinity, especially considering temperature effects.

The salinity on natural reefs has been discussed in previous articles. My recommendation is to maintain salinity at a natural level. If the organisms in the aquarium are from brackish environments with lower salinity, or from the Red Sea with higher salinity, selecting something other than 35 ppt may make good sense. Otherwise, I suggest targeting a salinity of 35 ppt (specific gravity = 1.0264; conductivity = 53 mS/cm).

Fortunately, coral reef aquaria seem rather forgiving with respect to salinity. The range of salinities encountered in what most would proclaim as successful reef aquaria is actually quite large. Don’t agonize over small deviations from natural seawater. You will not notice any benefit changing from 36 or 34 ppt to 35 ppt (specific gravity = 1.0256 to 1.0271). Many fine reef aquaria appear to run at salinity levels as low as 31 ppt (specific gravity = 1.023), but bear in mind that the values that aquarists report (as well as your own measurements) are fairly likely to be inaccurate, so pushing the low or high end of the range may not be prudent.

Bear in mind that if aquarists target salinity values different than 35 ppt, the amounts of calcium, magnesium, alkalinity, etc., will all likely deviate from natural levels as well. For example, making artificial seawater to a low salinity will normally result in low values for these parameters and may require adjustments.

[Percula9]

Just get a refractometer and forget the hydrometer. Then you will know for sure.

[jbird69]

When I used to use a hydrometer I had to be very careful of micro bubbles causing the swing arm to float and give a false reading.

[hippyman]

When I used to use a hydrometer I had to be very careful of micro bubbles causing the swing arm to float and give a false reading.

How do u keep that from happening?

[nano427]

I would recommend a refractometer, but if you want to use your hydro then take it to the lfs to have it checked for accuracy. I had my hydro meter checked today and it was off .004

[Randy Holmes-Farley]

You can also make a DIY test solution for it, especially if you have a balance:

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

[hippyman]

ok, heres my main problem, when I fill the hydrometer up to test, the meter automatically goes to the top, then doesnt come down. I originally thought this could be due to air bubbles, but according to the instructions, tapping on it with a pencil should have fixed that. It didnt. Am I doing something wrong?

[vegaskid11]

If there are bubbles on the arm you can see them.

[Randy Holmes-Farley]

Do you see air bubbles?

[hippyman]

Do you see air bubbles?

no, I dont see air bubbles, but after tapping it, it ended up reading around a 28

[Randy Holmes-Farley]

What did? The tank water or a standard?

[hippyman]

The hydrometer ended up reading a 1.028

[Randy Holmes-Farley]

Yes, but testing what water? Your tank water?

[hippyman]

Yes, but testing what water? Your tank water?

Oh, yes, I'm testing the tank water

[chuckreef]

You might try soaking the hydrometer overnight in a highly saturated salt solution, then rinse it a few times. Initially, the palstic floats (arms) are very prone to catching air bubbles, this subsides overtime.

Also beware that you must rinse these devices after each use. If you don't, overtime, they tend to start to read off (usually low due to salt adhereing to the floats).

[Randy Holmes-Farley]

It could easily be sg = 1.028. :)

[rustyjames]

Somewhat off topic, to make my own calibration fluid the article said to filll a 2 litre coke bottle to the brim, what would that measure exactly? I have litre measures, I guess 2 litres plus about 1/2 cup? Would like to see just how "off" my hydrometer is.

[bertoni]

The article lists the computed volume of a bottle. :)

http://reefkeeping.com/issues/2004-06/rhf/index.htm

2104.4 g. :)

[luconi]

I just started using a marineland InstantOcean hydrometer, but I'm not sure I'm using it right. I saw the woman at the LFS use it, to measure my test sample, which let me know my salt level was too high, but now, I cant get it down, even after all I did. The other night, I took out 5 gallons of salt water, and put in 5 gallons of fresh, now they said this should have fixed it, however, in my 75g tank, I'm still measuring too high of a salt content. Could I be using the hydrometer wrong, or could it be malfunctioning?

I would definitely suggest investing in a refractometer . I got mine for only like $35. !!Make sure you get an auto-temperature controlled (ATC) one!!, and a pretty good brand. I got one and I'm very glad I got it. It's accurate and I highly suggest getting one because accurately measuring the salt is one of the most important parts of owning a saltwater fish tank, of course. I hope this helped!

Here-- Check this one out- you should probably check out some more, but this one is probably good. Especially because this is from a top seller with 100% positive feedback http://cgi.ebay.com/New-ATC-Salinity-s-g-Refractometer-4-Aquarium_W0QQitemZ200438486581QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2eab109635

[Randy Holmes-Farley]

Rustyjames:

I would only use the Coke bottle method for gross checking, Using a balance makes a perfect standard, but the volume measurements are not exact since Coke bottles may vary a bit. :)