# Drop Checker Constantly Yellow



## Terry (27 May 2009)

Guys,
Problem is that the Drop Checker is now constantly showing yellow.  I use the 4 dkh solution from AE which is normally changed every other water change (fortnightly) but this last change it went from blue to green after a few hours (as normal) and remained green for about 3 days but then slowly turned yellow.  CO2 is switched off at night via solenoid.  I've even turned the CO2 off during the day and it still remains yellow.  I've changed the solution but the above process is repeated.

My guess is the 4dkh solution is suspect and will order some more from AE.  Has anyone else experienced this problem?


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## George Farmer (27 May 2009)

I think Dan Crawford had similar issues with an older batch of solution.  Try PMing him.


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## squiggley (27 May 2009)

I had the same problem, even with the co2 on as low as possible by dc would turn and stay yellow. the 4dkh was found to be duff


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## Terry (28 May 2009)

Thanks guys.  new solution ordered.


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## mjenner (29 May 2009)

Agh, cheers for this... I've got a little algae infestation resulting from this little problem in my tank, do you know if there's any care advice regarding storing the 4DkH solution?  My solution is in the tank cupboard which gets a little hot (broadband router and cordless phone base station are both stored in there, along with the power adaptors for the solenoid and the filter), any idea if that might have made the solution go bad as I think it did work initially when I first got it? Although now I think about it, in the early days I was running with the CO2 pretty wide open to try and help the plants establish themselves as the tank was fish-less in those days.


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## ceg4048 (29 May 2009)

mjenner,
             There is nothing magical or special about 4dkh "solution". It is either distilled, or RO water which someone then adjusts the alkalinity to 4dkh, or a concentration of  71.382 milligram per liter (ppm) of carbonate/bi-carbonate. This can be accomplished by using baking soda, and in fact, many people make their own 4dkh water in exactly this manner (although it's difficult to get t exactly right). You can drink 4dkh "solution" and it tastes better than that bottle of Evian sitting in the fridge.

It just so happens that when enough acid is added to this water to bring the pH down to 6.6 it turns a light green when a pH reagent is added. If the person who made this solution did not add enough baking soda then the concentration of carbonates in the water will be less than 4 dkh (less than 71.382ppm). With less baking soda in solution the water turns acidic much more quickly so that when pH reagent is added it turns green and then yellow at a higher pH.

It's easy to surmise that if the 4 dkh solution was duff, it was because it was NOT 4dkh and was actually 3, 2 or even 1 dkh instead.

Because this stuff is just plain old water there is no effect of it being warmer in the cupboard (unless it spills onto the router.) There is no "going bad". If the solution was properly mixed 4dkh water and f it sat in that cupboard for the next 100 years it would be just as effective because it's just water mixed with baking soda. 8) 

Cheers,


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## mjenner (29 May 2009)

Thanks Ceg,

Hmm, I did think that might be the case... but I couldn't think of why I thought it worked initially but now I'm seeing this issue.  I think it may well have been because I was using higher CO2 levels earlier and was expecting a yellow dropchecker (DOH).

Hmm, guess I'll have to order some more, it's a bit of a pain though, probably can't really prove that it was duff unless I send it back, oh well that's Â£4.99 down the drain... (literally  :? )

Once I stabilise the CO2 hopefully it'll help with my latest algae outbreak (Rhizoclonium I think). (levels have fluctuated of late as my needle valves were tinkered with by someone I think during we party I had recently...  trying to find the right level again and having a duff indicator doesn't really help).

Cheers,

Matt


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## Terry (29 May 2009)

Ceg



			
				ceg4048 said:
			
		

> mjenner,
> Because this stuff is just plain old water there is no effect of it being warmer in the cupboard (unless it spills onto the router.) There is no "going bad". If the solution was properly mixed 4dkh water and f it sat in that cupboard for the next 100 years it would be just as effective because it's just water mixed with baking soda. 8)
> 
> Cheers,



If there is no 'going bad' with the 4dkh solution what could be the cause of the drop checker mixture showing constantly yellow as explained in the original post?  Could it be the PH reagent that's at fault?


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## ceg4048 (30 May 2009)

Terry said:
			
		

> Ceg
> 
> If there is no 'going bad' with the 4dkh solution what could be the cause of the drop checker mixture showing constantly yellow as explained in the original post?  Could it be the PH reagent that's at fault?


Well, pH reagents have been known to be corrupt so I wouldn't rule it out, but as I said in the previous post someone could have prepared the solution to have an alkalinity of lower than 4. So although 4dkh water doesn't "go bad" it could easily have been _prepared_ bad. If it's less than 4 the reagent will turn the solution yellow when it should be green and green when it should be blue. There is an easy and obvious way to check this and that's to simply measure the KH of the solution with a KH test kit if you have one. Of course, it should measure 4.

Another possibility is that either the test vial or the 4dkh solution is corrupted by an acid. Have you or do you clean the vial with an acidic product such as vinegar or citrus juice? Measure the pH of the 4dkh solution directly by placing a sample in a different clean/dry test vial. Straight out of the bottle, the sample should measure very near 7 pH. If the pH of a sample of the solution is lower than 7 and/or if it measures lower than 4 dkh then the solution is faulty.

If the solution measures correctly then one has to move suspicion to pH reagent or acid ingress into the vial. What happens when the yellow fluid is removed from the tank and allowed to sit outside the tank for a few hours? If the yellowing is due strictly to CO2 then after a few hours the CO2 will outgas from the vial and the solution should turn to green and then blue-green. If it stays yellow then this means another acid may be present in the fluid. Check you pH reagent by measuring the pH of your tap water straight out of the tap. Let the tap water sit for a few hours. Measure this water again. Tap water has some CO2 which also outgases after a few hours so the reagent should register a different pH straight from tap versus sitting for a few hours.

Acid ingress while the vial is in the tank is the only other possibility. Could it be that the vial is bumped or displaced allowing tank water to infiltrate? Any wise guy with sticky fingers can perpetrate this crime in seconds with no one the wiser.

Cheers,


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## squiggley (30 May 2009)

What drop checker do you have?

I have beeb using the JBL type until I had a few problems with it coming unstuck so ordered a cheapy from ebay.

http://cgi.ebay.co.uk/Brand-New-Dro...34.c0.m14.l1262&_trkparms=|301:0|293:1|294:30

When it finally arrived I filled it with 4dkh + ph reagent and placed besides the JBL one which was lime green/yellowish.

Later when I came to do a water change I noticed that the new dc was light green whilst the JBL was now yellow.  I wanted to move a few thing around so most of the water was removed which exposed the DC to the air. After about 2 hours I noticed that the new DC was blue yet the JBL was still yellow.

The solutions in the two were made from the same bottle of 4dkh and ph reagent but made anout 3 days apart.

It made me wonder if tank water is making its way into the JBL DC either through a crack or dodgy o-ring.


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