Why does the salinity keep dropping on my 20g?

[aqh88]

Is it just my hydrometer? I have a floating hydrometer until I save up enough money for a refractometer. I rinse it through the storage container of ro water after every use. The tank has a penguin 330 powerfilter, small water pump, 100w heater, 1" of sand, and so far 5lbs of rock. I'm using reef crystals salt.

Day 1: measured sg at 1.022 so added 3lbs rock and sand

Day 2: measured sg at 1.020 so added more salt to make 1.022 again

Day 3: same thing

Day 4: measured sg at 1.016 got tired of it and raised the sg all the way up to 1.025

Day 4: sg still 1.025 picked up another 2lbs rock because I was bored and at the store anyway

Day 5: measured sg at 1.024

Day 6: sg at 1.022

 

It's getting annoying. Is the salinity changing or am I just getting messed up readings?

[Travis]

Bad Hydrometer.

 

Get a Refractometer. http://www.drsfosterandsmith.com/ have a sale on them, you can get one for like $39.99 + Shipping.

[Llamaguy]

maybe the temp is going up or down, don't remember the relationship.

[vyger]

Just to show the difference my tank @ 80deg...is 1.023 with swing arm hydrometer and 1.0265 with my refractometer. Talk about innacurate!Get a refractometer and you'll never use that thing again..

[ringfinger]

I have the same problem with the swing arm hydrometer. I'm using for my 2.5 gallon...should have known there might be accuracy concerns. I guess a refractometer is one of those things you should just buy from the beginning.

[Llamaguy]

maybe there should be a group buy on them I could spend $30 on one, but can't spare 60-80

[aqh88]

I don't have a swing arm hydrometer though. It's a floating one and it said nothing about adjusting for temperature. The temperature has also stayed the same on both my seperate glass thermometer and the one on the bottom of the hydrometer since the first day.

I already had the drfostersmith hydrometer in a saved order so I just went ahead and put it on the credit card. This is too inaccurate for me to feel safe putting anything else in the tank.

[Big Al]

I don't have a swing arm hydrometer though. It's a floating one and it said nothing about adjusting for temperature. The temperature has also stayed the same on both my seperate glass thermometer and the one on the bottom of the hydrometer since the first day.

I already had the drfostersmith hydrometer in a saved order so I just went ahead and put it on the credit card. This is too inaccurate for me to feel safe putting anything else in the tank.

 

My swing arm was reading 1.024 and had been for weeks I got a refractometer yesterday and found that my tank was actually at 1.030. Make sure you calibrate the refractometer when it comes.

[vyger]

I don't have a swing arm hydrometer though. It's a floating one and it said nothing about adjusting for temperature. The temperature has also stayed the same on both my seperate glass thermometer and the one on the bottom of the hydrometer since the first day.

Sorry LOL ...I musta read your post too fast...floating hydrometers are used in Labs and are accurate ...they can be a llittle hard to read tho....where the miniscus is due to the surface tension of the water I guess and if your putting it in the tank it'll be moving some....a refractometer takes the guesswork out of it.

[MillerLite]

It might depend on the quality of the hydrometer though. Go with a refractometer..costs less than $40. Imagine how much money you have and will put into your reef. $40 seems to be a small price to keep such an important parameter stable. Quickest way to kill everything in your tank is by shocking the system with a water change at a different salinity.

 

Difficult to believe the salinity is dropping unless you have a tremendous amount of salt creep which is greater than the evaporation in your tank. Evaporation = increased salinity. More than likely its the hydrometer or the readings you are taking from the instrument. Good luck!