# Gravel raising pH?



## fishkid

I always thought that pea gravel was inert, but after reading  this article it appears as if though that is not the case, and that standard pea gravel has enough calcium to boost pH and water hardness. This is of concern to me because I keep softwater species such as cardinal tetras and otos. 

I've tested the pH of both the tank water and tap water using a liquid test kit (only option I have), and they appear to be around the same, with the tank water possibly being slightly more basic. Both are between 7.2 and 7.6 (around 7.4), and if there is any difference in pH it is very small. Is the small difference due to an insignificant amount of calcium in the gravel, or due to the age of the gravel, meaning that any pH boosts would have occurred already? Or could it be from other factors, such as decaying plant matter or the many vals I have in the tank using carbonates from the water? Also, the test was conducted an hour or two after the lights had turned off.

I have two types of gravel in the tank. The first type is white and brown pea gravel I put in the tank when it was first set up in 2003. The second is some Petco brand black gravel, which appears to be colored with the actual gravel being white. The black gravel was put into the tank two years ago.

I had originally put in the black gravel to cover up the lighter colored gravel, but now after pulling out a good amount of vals with established root systems, the white gravel is starting to show again and I am thinking about adding some more black gravel to cover it up. I am concerned that if I do so, the calcium in the new gravel may cause a pH boost detrimental to the fish. Am I being overly paranoid, or is that a real possibility?


Thanks to those who have read this far.


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## Byron

It depends upon the rock used in making the gravel. If calcareous rock was used, then the gravel or sand made from it will release hard minerals (calcium primarily, magnesium and others too) slowly but consistently and this will raise the GH and pH and likely the KH as well.

As an example, substrates like crushed coral, aragonite, dolomite, marble and some others are specifically used in marine tanks and rift lake cichlid tanks because they will significantly raise the GH and pH, and that is needed with these fish.

Sand and gravel made from quartz are usually inert, unless something else gets mixed in. Inert means the gravel/sand has no effect on water chemistry.

If you buy a prepared packaged aquarium substrate it will usually say on the bag if it affects the chemistry or not. For years I used the natural buffy-coloured aquarium gravel that was inert. I am now using play sand which is inert. I had one tank set up for a year with what they call birdseye gravel, which is the darker type of pea gravel, and it was inert; I tested it by placing some in a small spare tank with no fish for a couple weeks, and there was no rise in pH. You just have to know what mineral the substrate is made from.

Turning to your specific case, I would suggest replacing the gravel with sand, rather than adding more gravel. The white is always going to keep reappearing, and if you are after a more natural appearance, a uniform substrate is best. And play sand like Quikrete available from Home Depot or Lowe's works very well, and is very inexpensive. I now have this in 5 (soon to be 6) of my 7 tanks.

Byron.


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## fishkid

Thanks for the help. Since you mentioned the bag, I found the old bag that the black gravel came in. It says that the gravel will not affect the water chemistry, so I guess it is inert. However the white gravel was put in the tank in 2003, and the bag is long gone, so I don't know if it's inert or not. I imagine that after all this time

I have thought about replacing the gravel with sand before, but have no idea how one would do so. I'm also concerned about how my plants would cope with the process, especially a large crypt I've had for two years. And then there's the matter of what to use as a replacement. I'd rather have something that already has nutrients in it than a plain substrate where I would have to add root tabs.


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## Byron

fishkid said:


> Thanks for the help. Since you mentioned the bag, I found the old bag that the black gravel came in. It says that the gravel will not affect the water chemistry, so I guess it is inert. However the white gravel was put in the tank in 2003, and the bag is long gone, so I don't know if it's inert or not. I imagine that after all this time
> 
> I have thought about replacing the gravel with sand before, but have no idea how one would do so. I'm also concerned about how my plants would cope with the process, especially a large crypt I've had for two years. And then there's the matter of what to use as a replacement. I'd rather have something that already has nutrients in it than a plain substrate where I would have to add root tabs.


To perhaps save you a lot of money, I would not waste it on so-called enriched substrates. From my own experience with one of them, and from my reading of what more advanced planted tank aquarists have written, I do not see much value in these.

I have had Flourite for over 15 months now. I still have to dose the tank with Flourish Comprehensive twice weekly, the same as my sand-only substrate tanks. The larger swords are still struggling, much more than they do in my sand tanks that have Flourish Tabs added every 3 months. I cannot justify the cost of the Flourite substrate, and this month I intend tearing this tank down and resetting with play sand.

I think the enriched substrates might be of benefit in high-tech systems. And there may be some types that are of some benefit. They are very expensive, and I do not have the desire to waste hundreds of dollars on one of these when I can use sand for less than $20 with equally-good if not better results.

There is also the fish to consider; some of these products actually tell you not to use them with substrate fish that like to dig or sift. And both Flourite and Eco-complete are too rough for corys and loaches; I saw problems with my corys that were in the Flourite tank and after i moved them to a sand tank they healed and recovered.


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## fishkid

I guess if I do change the substrate I will just go with regular sand then. Is it possible to use soil under the sand?

Also, how exactly does one change a tank's substrate? The tank is a 46 gallon tank so there is a fair amount of it, and I imagine the process would put stress on the fish and plants.


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## Byron

fishkid said:


> I guess if I do change the substrate I will just go with regular sand then. Is it possible to use soil under the sand?
> 
> Also, how exactly does one change a tank's substrate? The tank is a 46 gallon tank so there is a fair amount of it, and I imagine the process would put stress on the fish and plants.


I would not mess with soil.:lol: That too is of limited benefit. A fine gravel cap of 2 inches over a 1-inch soil layer is what most sources suggest, as sand tends to mix much more readily with soil. And again, if you have substrate-moving fish this can be messy.

A plain sand or fine gravel on its own is the best substrate. I've changed over my tanks many times over the years. The easiest is to move the fish into a temporary tank, a 20g will usually suffice. I fill it with water from the main tank (before disturbing anything), then move over the hardscape (wood, rock), sometimes some of the plants, then net the fish over. Most of the plants I just lay in a container and cover with water. This is a day process to do carefully and unrushed, so choose a day when you will be free of all other issues.


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## fishkid

I have a 15 and 10 gallon tank already running that I could put the fish in. They don't really have much in them except for plants and two shrimp in one and a few small tetras in the other. Would I have to acclimate the fish to the other tanks? All of my tanks use dechlorinated tap water. Also, how could I minimize stress to well-rooted plants? I have a two year old big crypt that I don't want to lose or have grow back stunted.

How do you recommend I wash out the sand? In the past when I've put washed substrates in a tank the water is still cloudy for a day or two. Will I have to remove the water from the tank before putting the substrate in?

Also, with the old substrate gone, would there be a risk of the fishes' bioload becoming too much for the tank?


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## Byron

> I have a 15 and 10 gallon tank already running that I could put the fish in. They don't really have much in them except for plants and two shrimp in one and a few small tetras in the other. Would I have to acclimate the fish to the other tanks? All of my tanks use dechlorinated tap water.


Yes, sort of. What I do is get the new substrate in, then arrange the hard scape (wood, rock). Keeping this in the old tank water until ready will keep the bacteria, then just make sure the water in the new tank is dechlorinated before putting any of the hard scape or plants in. At this point I do a 50% water change on the temporary tank where the fish are. When the new tank is planted, sometimes i drain it to remove the sediment stirred up, then fill with fresh tap water using the conditioner (dechlorinator). If the temp is the same, or it can be a tad warmer in the new tank, and the pH matches (GH will), I net over the fish.



> Also, how could I minimize stress to well-rooted plants? I have a two year old big crypt that I don't want to lose or have grow back stunted.


Most plants won't be affected, or very slightly, except for crypts. Most will melt, but come back.



> How do you recommend I wash out the sand? In the past when I've put washed substrates in a tank the water is still cloudy for a day or two. Will I have to remove the water from the tank before putting the substrate in?


Yes, the tank must be completely drained and the present substrate removed. Wash the sand well; outside with the hose and a bucket is easy. I find it is better rinsing only maybe 3-4 cups of sand at a time. When the sand is in the tank, I fill with about 6 inches of water, then siphon it out completely; this removes a lot of fine sediment. When the hard scape is done I add water to half or so, and plant (remember to dechlorinate the water). If this stirs it up bad, I drain it again and refill.



> Also, with the old substrate gone, would there be a risk of the fishes' bioload becoming too much for the tank?


With the plants, and the bacteria on the hard scape materials, plus the filter (I never rinse the filter at this time, but you can keep it running on the temporary tank), there shouldn't be any issue.


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## fishkid

I don't really have any hardscape at all, and the tanks I would put the fish into already have filters running on them. Would the bacteria in the filter be okay if the filter didn't run for the time I would need to swap out the substrate? 

Also, is there a specific brand and size of black sand you'd recommend that's easy to find at a place like Home Depot? I want to eventually keep cories in the tank so it'd have to be something that suits them.


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## Byron

fishkid said:


> I don't really have any hardscape at all, and the tanks I would put the fish into already have filters running on them. Would the bacteria in the filter be okay if the filter didn't run for the time I would need to swap out the substrate?
> 
> Also, is there a specific brand and size of black sand you'd recommend that's easy to find at a place like Home Depot? I want to eventually keep cories in the tank so it'd have to be something that suits them.


The bacteria is not an issue if there are sufficient live plants, particularly fast growing and here floating plants and stem plants are good. And provided the fish load is not great. I would just leave the filter on the tank (turned off obviously).

I use Quikrete Play Sand from Home Depot, you can see it in the photos under the "Aquariums" tab below my name on the left. It is a tan/gray/black/white mix that is near-identical to the sands in most Amazonian streams, so very authentic. My corys love it.

Byron.


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## fishkid

Is the sand dark enough to bring out the colors in the fish? Also, how much should I buy for a 46 gallon tank?


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## Byron

fishkid said:


> Is the sand dark enough to bring out the colors in the fish? Also, how much should I buy for a 46 gallon tank?


Yes. And one bag (which is 50 pounds or 25kg) will be sufficient, for a few dollars.


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## fishkid

Approximately how deep would the sand be if I used that amount? Would it be deep enough for swordplants and crypts?


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## Byron

fishkid said:


> Approximately how deep would the sand be if I used that amount? Would it be deep enough for swordplants and crypts?


You won't need all the bag, but playsand only comes in these bags. But having some extra for later, or another tank;-) is always nice.

I don't have more than 2 inches depth overall (level when first added). Then you can build up deeper areas (3 inches max) in the back for the larger swords. Rocks that are inert are best for this as they are less likely to shift, though in time all substrates will even out unless there is an underlying structure (I've never bothered with this).


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## fishkid

Thanks for all the advice Byron! I will probably get around to changing the substrate sometime next week.


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