Bleaching caps

[Riderc82]

Does anyone know why my montipora caps would all start to bleach at once?  It's weird everything is testing were it should be but for some reason in the last two weeks my five caps have all began to bleach (another weird thing is they all have good coloring around the outside edge where you generally see new growth).  The only thing that was changed in the last two months is that I have dropped my lighting from six hours a day to 3 hours a day.  I know three hours a day isn't much but I don't want my temperatures to exceed 81.  Another strange thing is all the acro's seem to be thriving and all my LPS look good.  I did notice the other night that I had quite a bit of salt creep on my halide bulbs so I wiped them down really good and reinstalled them.  The only other thing I can think is that two of the caps are touching but they have been touching for several months.  Any suggestions would be great.

[coral ranch]

Have you looked very closely to see if it might be monti eating nudies. They are very small and white so they blend in with the bleached out sections.

[Reefd Up]

Monti-eating nudis, double check your alkalinity, add some fans and bump up your light period, you're not vodka-dosing are you?  Your halide lamps are fully protected right (no UV burn?) 

It could also be lack of flow...you said it's the center of them...quite possible that's where the lowest flow is. 

[CoralBeauties]

May sound stupid but also check your salinity.  It is alot of time unchecked and can drift one way or the other.  My caps were doing the same a while back and I checked mine and it had drifted down to 1.20 from overfilling with topoff water.  Also my hydrometer reads 1.20 when my refracto reads 1.25.  Huge difference that could get you in trouble.
Jeff

[Riderc82]

I have been searching for bugs on them but can't find any and I haven't added any coral in at least 6 months.  I need to get a refractometer and double check the salinity, I currently use two Instant Ocean hydrometers. 

[jeremyt]

yes refractometers are crucial, hydrometers are sooooooooooooooo inaccurate

[UDJustin]

if you dont want to buy a refractometer ask to borrow one use it and see what it says compare it to your hydrometer and then just know that your hydrometer is off that much each time. Refractometers can be very inacurate too if not calibrated correctly on often.

[TechGuy]

yes refractometers are crucial, hydrometers are sooooooooooooooo inaccurate

Yeah, and not much more expensive. Locally like $45 or so. I think I paid $15 for my Hydrometer. Well worth the extar $30.

[micki]

if you dont want to buy a refractometer ask to borrow one use it and see what it says compare it to your hydrometer and then just know that your hydrometer is off that much each time. Refractometers can be very inacurate too if not calibrated correctly on often.

In my experience, hydrometers will vary from each reading each time so I don't think your idea would work.

[jeremyt]

yeah, i have 4 hydrometers 2 instant ocean and 2 coralife. 2 were just cleaned (one of each brand) and two brand new, get 4 different readings. . had to get a refractometer.

[rayviv]

My refractometer had a rusted hinge-pin  that affected readings. Got a new one w/lite and got the other one fixed. Calibrated both and the old one reads the same as hydrometer while the new one reads 3pts higher. Both have been recalibrated 3x.

Paid 45.00 for the old one, 90.00 for the lighted one.

JM2c   

[lazylivin]

My refractometer had a rusted hinge-pin  that affected readings. Got a new one w/lite and got the other one fixed. Calibrated both and the old one reads the same as hydrometer while the new one reads 3pts higher. Both have been recalibrated 3x.

Paid 45.00 for the old one, 90.00 for the lighted one.

JM2c  

What are you calibrating it with? As per the directions with Distilled Water (0-TDS)? If so consider getting 35ppt calibration fluid. I calibrated three refractometers to 0 using distilled water and got three different readings. And they weren't even close. Bought 35ppt calibration fluid, recalibrated and they were 100% exactly the same. Calibrating to 0 is so far from the range of our reef tanks that the margin of error increases exponentially.

IMO hydrometers are just as consistent as a refractometer, it is just that a refractometer can be calibrated. So if you have a friend that has a properly calibrated refractometer have them compare to your hydrometer and mark the actual 35ppt or whatever your goal salinity is with a marker on your hydrometer and you should be just fine.

[Reefd Up]

The biggest problem with hydrometers is that how they measure varies with temperature.  Most manufacturerers calibrate their hydrometers in the 60-70 degree range (where very few people keep their tanks.)  Additionally, there are no cross reference plots to compare different temperatures to different salinities (I started testing this, but no one seemed to care.)  From calling hydrometer manufacturers, the manufacturers didn't even seem to know much about the calibration (large variation of temperature calibration from batch to batch.)

So, say you have saltwater at 70 degrees...and it tests at X.  If you take the same water (no evaporation) at 80 degrees, it'll be different.  You can also take 2 different brand hydrometers in the same water...and they'll show different salinities usually.  A refractometer will show the  salinity without regard to temperature.

[lazylivin]

With all due respect Nickii, refractometers or more effected by temperature.

When it comes to field testing (Outside) Temperature is one of the single most important factors influencing accurate refractometer readings and is one of the largest sources of error in measurement with the exception of calibration in the wrong range detailed above. Refractive index is VERY dependent on temperature. It is well known that substantially all materials expand when heated (become less dense) and contract when cooled (become more dense). The speed of light in a liquid increases with temperature, and the refractive index, therefore, decreases.

IMO all of our tanks range from 76-82 degrees which will give us consistent readings which is most important.

[micki]

Those are interesting thoughts...When I make up new salt water the temp is always cold like 50-60 degrees.  I've always tested it cold then heated it up to match my tank temp.  I also recheck the salinity after it's heated up and I have always gotten the same reading as the cold water.  So, for me temp. doesn't seem to be an issue with my refractometer.

[UDJustin]

thats why i bought a salinity meter just calibrate it put the probe in the water and read the digital display lol

[Reefd Up]

With all due respect Nickii, refractometers or more effected by temperature.

When it comes to field testing (Outside) Temperature is one of the single most important factors influencing accurate refractometer readings and is one of the largest sources of error in measurement with the exception of calibration in the wrong range detailed above. Refractive index is VERY dependent on temperature. It is well known that substantially all materials expand when heated (become less dense) and contract when cooled (become more dense). The speed of light in a liquid increases with temperature, and the refractive index, therefore, decreases.

IMO all of our tanks range from 76-82 degrees which will give us consistent readings which is most important.

I don't think I explained myself well.  Yes, they are affected by temperature, but can be compensated for since they can be properly calibrated...whereas hydrometers are permanently calibrated.  Hydrometers are calibrated during production and cannot be changed.  Refractometers are calibrated initially too, but they can be re-calibrated to compensate for temperature variations.  Like you said, our aquariums are pretty stable. 

[lazylivin]

I agree with your statement Nickii. However one way to calibrate a Hydrometer is with a black magic marker. 

Micki, I think the reason we dont see Salinity variations with temperature in this case is because your Refractometer is always room temp. So if you put a drop of 60 degree or 80 degree water on it, close the lid...it  is the same temp (room temp) in a couple of seconds. Try putting the refractometer and Hydrometer in the refrigerator for an hour and then test.

[lazylivin]

thats why i bought a salinity meter just calibrate it put the probe in the water and read the digital display lol

Show off 

[UDJustin]

hey it wasnt too much more than a good refractometer lol