Low specific gravity, please be very specific with advice

Hi all, it seems I just can't get my water chemistry right. Had a salinity spike 11/2/11. Over compensated that day and had it down to 1.021. Ever since I can't get it right, need help before more stuff dies. Got it up to 1.023 by 11/4/11. Stopped adding anything, LFS said this is pefect target number. 11/6/11 it went up to 1.026 & I got scared it was too high again cuz a lot of stuff died in original spike. Took out 2 cups salt water, added 2 cups fresh water, found out later from you guys this rate was actually OK. (Why do the hydrometers make it look like this is too high? Original spike was off the charts high) it stayed steady at 1.022, but I know that's still too low for corals so I added 3cups water at 1.024 on 11/8/11. Next morn it was between 1.023/4, so I did nothing, figured evap would take care of the rest. Next day(11/10/11) back down to 1.022/3. It stayed steady there until yesterday (11/13/11). I've been taking readings twice a day since the spike, yester morn it was up to 1.023/4, then last night dropped off to 1.020. (WHY? I haven't added any water at all since 11/8/11. I did use Kent's phosphate sponge though, will this take out salt too?) So last night added 4 cups at 1.026. This morn still at 1.020, so I added 2 more cups at 1.026. That was 4 hours ago and still reading 1.020. This is a 29 gallon biocube. My amonia is 0.0, nitrates are less than 0.2 (lowest chip on my test) but Ph is low at 8.0 and nitrates a little high at 20 m/l. I'm due for 5 gal water change on 11/17/11. I'm thinking my best bet is to do it a few days early and hopefully this will stabilize everything. I don't mix my own water, I buy it from LFS. I have to get this stable, it's not good for my babies. Please advise...

 

First of all, I'd recommend dumping the hydrometer for a refracometer. I wouldn't be surprised if some of your readings had to do with inaccuracies based on this.

Whenever I have salinity that isn't perfect, I try to correct everything slowly. I think the rapid changes are more harmful than slightly high or slightly low salinity.

Additionally, to raise salinity, I top off with water that is at the salinity I want (instead of adding a "higher salinity" water to raise overall salinity).

Lastly, an ATO is a life saver, and makes things much easier. I'd highly recommend one if you're having trouble keeping salinity correct due to evaporation.

Note: I keep my salinity at 1.025. So at 1.026 you shouldn't be too concerned I wouldnt think.

 

Is the top of your tank covered? How much evap do you have a day? Like stated above, if you are having a large amount of evap everyday, then an ATO would really benefit you.

 

Sounds to me like your using a hydrometer that is getting bubbles stuck on it or something.

 

@Mobilized~ That's what I thought too, been double checking each reading 2-3 times and checking for bubbles each time since 11/6/11. if 2 or 3 in a row come back the same and I don't see bubbles, I figure that's not it.

@Sticksmith~ Yes my tank is covered, I usually have very little evap. sometimes a cup a day, mostly less than that. The part I don't understand is the sudden drop.

@Zechenia~ Yes, the initial spike was from improper top offs. I would think if evap was the prob that my salinity would be too high though and it's been too low for too long. The first corrections I tried were adding water at 1.024 which is about where I wanted it, but since it still dropped again, I used a higher specific gravity this time. I just don't understand why it keeps dropping. I've added NO water that was lower than 1.024 since 11/8/11. I just can't seem to get it to come back up and stay there. I will look into a refractometer as you sugested. I did also borrow another hydrometer to copare to mine and there was very little difference between them.

 

Are you running a skimmer? If so running it wet will drop your salinity. Salt creep from some sort of splashing. I agree hydrometers are not very reliable.

 

Refractometer for reading salinity w/ Free Calibration fluid - English

Best $40 you'll spend

 

Thanks Nanareefer. Yes I run the only skimmer I know of that will fit in the biocube. What do you mean by "running it wet"? The instructions only give one way of setting it up. Should I just stop running it altogeather to stop this? I really need to get my specific gravity up and keep it there. I am def going to invest in a refractometer. Once again, not the best advice from my LFS. Wish I'd found this forum sooner.

 

Also, what is an ATO?

 

Automatic Top Off, used to replace water in either you DT or sump as the water level starts to fall under a certain level.