Gravel increasing KH, GH and pH levels

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dezcookies

Aquarium Advice Apprentice
Joined
Oct 15, 2014
Messages
39
Location
Darwin, NT, Australia
Sorry for long post but thank you so much for those that will take the time to read and give me any feedback. Here goes.

I bought some smooth peach/rose colour (color) gravel from a stonemason over a month ago. I spent 3 hours washing 40kgs (88.2lbs) of gravel in small batches for quality control. When I added it to the tank I did a 80% water change.
I have been doing 40%PWC every 4 days with gravel cleaning but I haven't had time in the last 10 days. I noticed my pH rose from 7.6 to 8.4 (I didn't notice it earlier since I was busy with exams).

Immediately checked all my parametres (parameters) for any abnormality. My ammonia, nitrate and nitrite were fine but my GH and KH rose significantly.

The readings for my tank currently are:
pH - 8.4
GH - 196.9ppm (11 drops of API GH test solution)
KH - 143.2ppm (8 drops of API KH test solution)



Water that comes from my tap(which i used initially to fill the tank) have readings of:
pH - 7
GH - 71.6ppm (4 drops of API GH test solution)
KH - 53.7ppm (3 drops of API KH test solution)



Now I am wondering if a tank is dirty (some excess food+fish poop) and haven't had any PWC for last 10 days, will that raise the GH and KH levels?

I am currently testing the gravel in a separate container starting from wednesday. The readings initially was same as above when it came out of the tap but in the last 72 hours, the isolated gravel sample's reading increased to:
GH - 89.5ppm (5 drops of API GH test solution)
KH - 71.6ppm (4 drops of API KH test solution)


I believe it may be the gravel that's releasing minerals into the water however my isolated sample will tell me in a weeks time (giving it 1 week just to see any significant increase in minerals).


Any thoughts on this anyone?

also I would like confirmation that missing weekly PWC will not result in increased GH, KH and pH.
 
Missing weekly water changes should not increase, GH, KH or pH. In fact, if you missed too many it would likely decrease KH and pH.

Do you know what type of rock the gravel is made from?
 
Unfortunately not. I bought the rocks as they looked identical to the lfs stock. Also an employee from the lfs told me they get it from the stonemason. I will be removing the gravel tomorrow and having a bare bottom tank for a while until my isolated gravel experiment tells me it's safe to use those gravel.
 
It is probably calcareous rock. Try putting some vinegar on it, and if you see some reaction it is definitely calcareous. However vinegar is not strong enough to detect all calcareous rocks, in some cases you need a stronger acid, but since it raised your pH and hardness significantly I wouldn't be surprised if it reacted to vinegar.

If you want to be sure it is the rocks that are changing the parameters just do a simple experiment. Take 2 buckets filled with tap water, and put rocks in one of them. Wait some time then test the water from both buckets.
 
If you want to be sure it is the rocks that are changing the parameters just do a simple experiment. Take 2 buckets filled with tap water, and put rocks in one of them. Wait some time then test the water from both buckets.


I am doing that experiment with an isolated container with the gravel. The results did go up but it was only 72 hours. Will be expecting conclusive results on Wednesday. I'll give the vinegar test a go tomorrow. Results will be up in 14 hours.
 
I did the vinegar test today. I have rocks that aren't inert :(
Did a full tank clean and removed all gravel. The water looks clearer now. Thanks for your advice :)
 
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