Instant ocean hydrometer accuracy?

[Cory p]

I don't have a refractometer at the moment but I have a instant ocean hydrometer,how accurate is it? I made water for first time today and on got a 1.023 reading but I don't want to use water if it's not accurate as a refractometer. Any help would be appreciated

 

[Sabellafella]

I don't have a refractometer at the moment but I have a instant ocean hydrometer,how accurate is it? I made water for first time today and on got a 1.003 reading but I don't want to use water if it's not accurate as a refractometer. Any help would be appreciated

To tell you the truth. Theyre all different, i would mix a known amount of salt to water to give you a standard (1.025) then use this as a baseline. They work, but every single one ive layed eyes on are absolutely not reliable

 

[nemo1017]

If I were you I would get a refractometer asap. You'll drive yourself nuts with that hydrometer...just my experience lol.

 

[Cory p]

To tell you the truth. Theyre all different, i would mix a known amount of salt to water to give you a standard (1.025) then use this as a baseline. They work, but every single one ive layed eyes on are absolutely not reliable

Sorry I put 1.003,I meant to put 1.023. I need water asap and have some made now but cant get my hands on refractometer til friday

 

[Jerry Barnes]

I've found mine to be very close to my refrac. I use it when mixing salt. Check my tank with the refrac. I'm surprised how accurate it I'd.

 

[Cory p]

I've found mine to be very close to my refrac. I use it when mixing salt. Check my tank with the refrac. I'm surprised how accurate it I'd.[/QU

WHEN using hydrometer is it usually lower or higher reading from you refractometer?

 

[Sabellafella]

Sorry I put 1.003,I meant to put 1.023. I need water asap and have some made now but cant get my hands on refractometer til friday

I would still use the water lol if your filling the tank thats fine. If your doing a wc, match the reading with temperature and you should be ok

 

[donnievaz]

Mine is really close, I was very surprised. Still, get the refractometer ASAP.

 

[Cory p]

Mine is really close, I was very surprised. Still, get the refractometer ASAP.

I have one on the way,I figured it would be alright to use for now. I just wanted to see who's used one and how accurate they are. Don't want to put water in my tank that's the right salinity

 

[Fishyj]

I had one. I was using it when I made new water. It worked great until my corals started to have problems. I took my water to my lfs and found out even though it was reading 1.026 it really was 1.038. I ordered a refractometer from Amazon that day. Really for what they cost, it's about the price of a nice fish or coral.

 

[Jerry Barnes]

Are these new electronic salinity devices any good or are they hassle due to always having to be calibrated? Seems like the future but I haven't had any first hand experience with them.

 

[ebushrow]

there are many things that can "throw off" a reading on a hydrometer....things like bubbles on the arm, calcium build up, etc. If you need to use a hydrometer a good practice if to thoroughly wash it with RODI and vinegar after each use. Then verify when you use it that there are no bubbles on the arm and no white spots or undissolved particles...in case your refractometer takes longer to get.

 

[MaiReef]

If rinsed, they seem to work fine. Just check for bubbles or debris. I haven't had a problem.

 

[tomtom2245]

I used one for years with no problems. I was diligent about rinsing it with RO/DI water after each use though. Prevents buildup around the swing arm that can throw off your readings.

 

[Randy Holmes-Farley]

You can make a DIY test fluid to verify it here:

Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-06/rhf/index.htm

A 3.714 weight percent sodium chloride solution matches 35 ppt (sg = 1.0264) seawater for use with a hydrometer.

To produce a 3.714 weight percent sodium chloride solution, dissolve 1 teaspoon (6.20 grams) of Morton's Iodized Salt in 161 mL (161 g) of fresh water (making a total volume of about 163 mL after dissolution of the salt). This solution can be scaled up as desired.

For a rougher measurement in the absence of an accurate water volume measurement:

1. Measure ¼ cup of Morton's Iodized Salt (about 73.1 g)
2. Add 1½ teaspoon of salt (making about 82.4 g total salt)
3. Measure the full volume of a plastic 2-L Coke or Diet Coke bottle filled with purified fresh water (about 2104.4 g)
4. Add an additional 2 tablespoons of purified fresh water (about 30 g)
5. Dissolve the total salt (82.4 g) in the total water volume (2134.4 g) to make an approximately 3.7 weight percent solution of NaCl. The volume of this solution is larger than the Coke bottle, so dissolve it in another container.

How to Use a Specific Gravity Standard

Depending on the type of hydrometer, one would use this solution differently.

For standard floating hydrometers (Figure 2), which are not self-correcting for temperature variations, it is important to use the standard at the same temperature at which the aquarium water will be tested (within say, ± 0.5 ºC or ± 1 ºF). Preferably, that will also be the temperature at which the hydrometer is intended to be used (often marked on it), but that is not an absolute requirement. The aquarist can then mark on the hydrometer the level to which it rises (that is, the water line), and use that as an indication of the specific gravity of S=35 seawater, which has all of the properties listed in Table 1(specific gravity = 1.0264, etc). If the hydrometer reads higher or lower than 1.0264, then the aquarist can just imagine the scale on the hydrometer to be shifted self-correcting for temperaturevariations, add the standard to the swing arm hydrometer at roughly the same temperature at which the aquarium water will be tested (say, ± 5ºC or ± 10ºF). Once the reading stabilizes, the aquarist can mark the reading (or just remember it) and use that as an indication of the specific gravity of S=35 seawater, which has all of the properties listed in Table 1 (specific gravity = 1.0264, etc). If the hydrometer reads higher or lower than 1.0264, then the aquarist can just imagine the scale on the hydrometer to be shifted up or down, and shift all other readings taken with it by the same amount, just as for a standard floating hydrometer.

Just to be especially clear: this solution need not be used at exactly 20ºC (68ºF). It will be just about as accurate at 25ºC (77ºF) since specific gravity does not change much with temperature, and these salt solutions would be expected to change density with temperature in about the same fashion as seawater. The most important factor is that the temperature of the standard, when measured, be the same as the aquarium water when it is measured..

How to Use a Standard Hydrometer

Here are a few additional tips for using a hydrometer:

1. Make sure that the hydrometer is completely clean (no salt deposits) and that the part of the hydrometer above the water line is dry. Tossing it in so it sinks deeply and then bobs to the surface will leave water on the exposed part that will weigh down the hydrometer and give a falsely low specific gravity reading. Salt deposits above the water line will have the same effect. If any deposits won't easily dissolve, try washing it in dilute acid (such as vinegar or diluted muriatic acid).
2. Make sure that there are no air bubbles attached to the hydrometer. These will help buoy the hydrometer and yield a falsely high specific gravity reading.
3. Make sure that the hydrometer is the same temperature as the water (and preferably the air).
4. Read the hydrometer at the plane of the water's surface, not along the meniscus (Figure 2; the meniscus is the lip of water that either rises up along the shaft of the hydrometer, or curves down into the water, depending on the hydrophobicity of the hydrometer).
5. Rinse with purified freshwater after use to reduce deposits.
6. Do not leave the hydrometer floating around in the tank between uses. If left in the aquarium, deposits may form that will be difficult to remove.

How to Use a Swing Arm Hydrometer

In addition to those described above, here are some special tips for swing arm hydrometers:

7. Make sure that the hydrometer is completely level. A slight tilt to either side will change the reading.
8. Some swing arm hydrometers recommend "seasoning" the needle by filling it with water for 24 hours prior to use. This presumably permits the water absorbed into the plastic to reach equilibrium. In the case of the hydrometer that I tested in a previous article, the hydrometer became slightly less accurate after "seasoning."

 

[Jay_M]

Take it for what its worth, but i compared 2 side by side, rinsing first and clearing all air bubbles.

 

[-Logzor]

Same bought two as a back-up to test my water and both read totally different not matter how hard I try to remove bubbles and such.

 

[RJ Harris]

I use to have one and it was the worst thing ever. My cousin came over with his refractometer and it showed a huge difference. I threw it away right after that

 

[Reef man 89]

I have a IO and a Corallife hydrometer and they both are way off from each other. The IO will read 1.020 and the CL with read 1.028 so you really don't know

 

[brandon429]

hydrometers are all ive used for 16 yrs and wont ever need a refract, my swingarms are taken care of as mentioned above. every few years ill calibrate them to the LFS refract and its 1 point off on the high side, but very consistent and my reefs don't care. so, ill never buy a refractometer what worked in 2001 still good for my tiny reefs.