Tropical Fish Forum

Tropical Fish Keeping Help and Advice => Fishtank Filtration and Cycling => Topic started by: Nan on May 15, 2019, 01:33:24 PM

Title: Is it actually dolomite gravel?
Post by: Nan on May 15, 2019, 01:33:24 PM
Sourced a sample packet of something advertised as dolomite gravel from Amazon.co.uk. How can I tell if it's actually dolomite gravel and not just some generic white gravel?

I put a few washed grains into a spoon of vinegar and nothing happened. But I'm not sure it should have.

I have now put a few grains in a test-tube containing my very acidic (6.0 or lower) aquarium water and will retest the water in about 12 hours to see if there is a change.

Is there any other reliable way to know if this is actually dolomite gravel?
Title: Re: Is it actually dolomite gravel?
Post by: Sue on May 15, 2019, 01:58:40 PM
Unfortunately, I can't think of anything.

Vinegar doesn't always work as it's a weak acid (acetic acid).


Leaving some to stand in water should increase the pH slightly if it is dolomite - or even coral, aragonite etc. The way to be absolutely sure is to leave a second container with just water next to it and test that at the same time as the dolomite water. If the two waters stay the same, the gravel won't do anything for the tank but if the pH (and GH and KH) increase over a week compared to plain water it will help the tank.
Title: Re: Is it actually dolomite gravel?
Post by: Nan on May 17, 2019, 02:56:05 PM
Worth a try! :)
Title: Re: Is it actually dolomite gravel?
Post by: Nan on May 20, 2019, 09:05:50 PM
A few moments ago I thought I'd test the jar of water that I put the supposed dolomite chips in four days ago, and it came out more basic. (A noticeable color difference.) So I tested the water in the control jar and it also came out more basic than the tank water, and more basic than the water with the dolomite chips. (Noticeably so.)  I emptied the test tubes, washed everything, and tried again. Same result.

So I had another bucket of water that has sat out for 24 hours and it's down just around 6-ish. Ok, pwew, as that's what went in at the last water change. Double-checked the tank, 6-ish. All is good there.

So I checked the tap water. Straight out of the tap tonight it's turning the testing solution green - well into the 7 range, which it's never done before. So the question - does tap water change Ph that much from day to day? Or an I losing my mind?

I'm going to take the chips out and rinse them off in the "6" water and then put them in a fresh jar of water, and leave a jar of the same water for control.  Maybe it's the light - I finally opened a window and held the test tube and the color chart out there, as it seems that all our "inside" lights are LED. It was still showing up like that, though. (The higher Ph in the tap, the "dolomite" and the control.)
Title: Re: Is it actually dolomite gravel?
Post by: Sue on May 20, 2019, 09:59:39 PM
The pH of freshly run water and water that's been allowed to stand is rarely the same - that's why I suggested the container of plain water to test alongside the dolomite water.

The pH can change up or down on standing. Water with a lot of carbon dioxide dissolved it in has a lower pH when fresh than when allowed to stand. CO2 makes water acidic, but it gasses out on standing so the pH rises. And with acidic water, water companies often add something to increase the pH so that a low acidic pH doesn't corrode their pipes. Again, these things gas out over a few hours so the pH goes down.


The pH of the same type of water (fresh or stood) should remain constant from day to day - unless the water company has changed something.



But I have no idea why the plain water was more basic than the dolomite water  ???
Are the two containers the same? Could one be made of something that's affecting the pH? (picture me grasping at straws.....)
Title: Re: Is it actually dolomite gravel?
Post by: Nan on May 21, 2019, 09:43:04 AM
Yeah, that threw me, too. They are both Mason canning jars. They had been previously used, so I thought perhaps they might not be clean, and I washed them out with very hot water and started over. I also rinsed the beejeezus out of the gravel. I also have a second sample of gravel from the same company, so I may set that one up today too, just for curiosity's sake.

I had known about the C02, but not about the anti-corrosives. It's just interesting that I could get two such wildly different readings 48 hours apart, out of the same tap at the same time of the evening, after having let the water run for a bit.  I am going to test it again in a few minutes, just to see if perhaps the light was playing tricks on my eyes.
Title: Re: Is it actually dolomite gravel?
Post by: Sue on May 21, 2019, 09:48:33 AM
Just to check - you do wash the test tubes well, then dry them by poking a paper towel/tissue inside? And the lids.
Title: Re: Is it actually dolomite gravel?
Post by: Nan on May 21, 2019, 07:22:32 PM
I wash them in screaming hot water, and then let them air dry. Should I use the towels?
Title: Re: Is it actually dolomite gravel?
Post by: Sue on May 21, 2019, 07:33:03 PM
I dry them so that anything dissolved in the water is removed. If they air dry, any deposits will still be on the glass. I use a paper tissue (the kind for blowing your nose on). I take one corner and twist it round till it fits in the tube, then push it in and twist the tube round on it till it's dry.


I always wash tubes immediately after reading them and making a note of the number. Nitrite in particular stains the tube if left. I empty the tube and rinse it 3 times. Then I half fill, shake it well and empty 3 or 4 times. Then let it drain a couple of minutes and use the tissue. The lids are rinsed under the tap for about 20 seconds, then drained and dried.
Title: Re: Is it actually dolomite gravel?
Post by: Nan on May 21, 2019, 07:42:51 PM
Hmmm. Well, I don't leave them sitting out. So it's not that. Haven't tested anything else again (been crazy busy today) but I'll check again in the morning. It could be that the gravel is just gravel and not doing anything at all.

Title: Re: Is it actually dolomite gravel?
Post by: Nan on May 25, 2019, 06:39:27 PM
Ok, that first batch of gravel that gave me the wonky readings I tossed. I had gotten a second packet. I put it all (several tablespoons) in a Mason jar with water, put tap water in the other, and left it for five days. There is a very distinct rise in the Ph - the water is way up in 7- so it looks like this stuff is the real thing. I have sewn a small mesh bag and put two teaspoons of the gravel in it and it's hanging on the intake of the filter, at present. (Didn't want to deal with disassembling the filter to put it inside with the sponges.) Since the "Up" is only temporary and disappears overnight (seemingly) in the water, perhaps this will do better.

I did change about 25% of the water in the tank, to bring the ammonia down a bit.