# Question about my cap



## freeflow246 (Jul 24, 2011)

So I have about .5 inches of gravel over roughly an inch of dirt. When I siphon the gravel, some of the gravel is sucked up and down the tube and into the bucket, and some dirt too. Most of the gravel falls back down if I wiggle the siphon, but now dirt has been loosened into the aquarium and sometimes a small patch of dirt is left bare. I've also been dealing with brownish water and I've come to think that dirt is leeching into my water through my cap.

Should I add more gravel? Or is anything more than .5 inches not good?


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## umarnasir335 (Jan 9, 2014)

YES! Always have a thicker gravel cap than the dirt you're using. I wouldn't use anything less than 1 1/2 to 2 inches of a gravel cap.


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## Elvette Emmett (Aug 16, 2013)

I never like using gravel as my cap, the dirt always makes it through the gravel, I like sand better, it looks better too


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## freeflow246 (Jul 24, 2011)

GAHHHH I need to put more cap in then! Should I just... take everything out? Or shovel in more gravel and just pull the plants up a little bit?

I was thinking about going the sand route, but I've heard it can be difficult. :/


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## umarnasir335 (Jan 9, 2014)

Just ease the rest of the gravel in, a few pieces at a time. The larger your cap, the more you can get away with when planting and moving stuff around.

It doesnt matter if you use sand or gravel as a cap - they're both inert. In my opinion, sand could be a little iffy if you're doing bottom-sifting fish such as cory cats or plecos.


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## rpadgett37 (Jan 1, 2014)

I am hardly an expert on this type of setup; however, I have been studying quite a bit in preparation for an NPT of my own.

Having said that, soil based tanks rely heavily on bacteria in the soil to breakdown organics into nutrients usable by the plants, as well as nitrification. As such, you want water to sift through the cap to the soil so the bacteria can perform their function enabling plants to better perform their function in the tank.

A cap of 1.5 to 2 inches is too thick, particularly if you plan to use sand. A cap of that depth virtually guarantees your soil will become anaerobic, forcing plants to use a fermentation process to break down nutrients, releasing H2S into the surrounding soil and eventually into the water. Under these conditions, your plants will eventually melt away.

Soil at 1 inch in depth is very good. A gravel cap should be around 1 inch in depth, while sand, being a tighter cap, should be no thicker than .5 inches. You also want to leave the substrate alone, allowing for the bacteria to settle in and grow undisturbed so they can do their thing.

There's alot more going on here that I don't fully understand. Binding of heavy metals, introduction of minerals into the water for floating plants and fish, plant processes that help keep the soil aerobic. Perhaps someone else more knowledgeable could clarify that.


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## rpadgett37 (Jan 1, 2014)

Sorry for the double dip, but I left something out, the grain size of the gravel. Should be between 2-4mm. Standard aquarium gravel isn't really suitable (grains are much larger).

Lots of people use blasting grit, while others will use pool sand with a larger grain size. I personally plan to use Black Flourite from Seachem. Grain sizes are perfect.


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## lilnaugrim (Mar 27, 2013)

I've used gravel just fine for a cap, but yes you will lose a little bit of dirt when you siphon. It didn't bother me much since it was only a small 3 gallon NPT but it's up to you. I liked the gravel since it allowed my dirt to breathe and not become anaerobic.

As for the tea color, that's just the soil and the wood chips releasing tannins into the water, not the dirt clouding. It's normal for most/all NPT's.


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## freeflow246 (Jul 24, 2011)

My gravel IS aquarium gravel, but it's very fine. Almost like coarse sand. And when I say stained, I mean dark dark brown. Like, I can't see in unless I turn on the tank light. It was tea-colored after a 50% water change lol. Before that it was like a blackwater aquarium.


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## freeflow246 (Jul 24, 2011)

Oh and it's not so much getting up a bit of dirt that I mind, it's that siphoning seems to expose a patch of soil that then dirties my whole tank.


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## lilnaugrim (Mar 27, 2013)

umarnasir335 said:


> It doesnt matter if you use sand or gravel as a cap - they're both inert. In my opinion, sand could be a little iffy if you're doing bottom-sifting fish such as cory cats or plecos.


I just had a question as to why you think sand is iffy for catfish?



freeflow246 said:


> My gravel IS aquarium gravel, but it's very fine. Almost like coarse sand. And when I say stained, I mean dark dark brown. Like, I can't see in unless I turn on the tank light. It was tea-colored after a 50% water change lol. Before that it was like a blackwater aquarium.


Okay, could be then that the dirt is getting through and clouding up your water. My apologies for assuming it was tea stained only! I would certainly say though, bump up your gravel cap and do a few water changes to see if it helps in a few days.


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## freeflow246 (Jul 24, 2011)

Should I just drop more gravel in, or should I remove everything? And I purposefully didn't boil my driftwood, but there's no way it could be staining it THAT much lol.


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## lilnaugrim (Mar 27, 2013)

Meh, just put more gravel in unless you don't like the gravel! But I'd personally just throw more in.


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## kittenfish (Dec 1, 2013)

What kind of dirt did you use? Mine gets stirred up all the time but it clears up on its own in just a couple minutes. I actually have a thin layer of soil on top of my sand now from messing with the plants so much and it doesn't cloud the water at all.


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## freeflow246 (Jul 24, 2011)

Miracle Gro organic potting soil


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## umarnasir335 (Jan 9, 2014)

lilnaugrim said:


> I just had a question as to why you think sand is iffy for catfish?
> 
> 
> 
> Okay, could be then that the dirt is getting through and clouding up your water. My apologies for assuming it was tea stained only! I would certainly say though, bump up your gravel cap and do a few water changes to see if it helps in a few days.


Sand isn't iffy for catfish, actually it's better than gravel cuz they can sift through it. However, in a dirted tank, a big enough catfish and pleco could possible overturn enough of your cap that your dirt might be exposed. This is just food for thought. Dustin from Dustin's fishtanks on youtube runs cories on all his tanks and they do well with a gravel cap, though.

As for the poster talking about anaerobic bacteria build-up: the thicker cap does pose such a threat, but ONLY if you're going for the Walstaad method and planning a tank that runs itself. Part of any aquarist's routine would be to gravel vacuum every couple of weeks to prevent anaerobic bacteria from building up - this is also where the larger cap will come in handy.


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## lilnaugrim (Mar 27, 2013)

umarnasir335 said:


> Sand isn't iffy for catfish, actually it's better than gravel cuz they can sift through it. However, in a dirted tank, a big enough catfish and pleco could possible overturn enough of your cap that your dirt might be exposed. This is just food for thought. Dustin from Dustin's fishtanks on youtube runs cories on all his tanks and they do well with a gravel cap, though.
> 
> As for the poster talking about anaerobic bacteria build-up: the thicker cap does pose such a threat, but ONLY if you're going for the Walstaad method and planning a tank that runs itself. Part of any aquarist's routine would be to gravel vacuum every couple of weeks to prevent anaerobic bacteria from building up - this is also where the larger cap will come in handy.


Yes, I am aware which is why I wondered why you said it was iffy. However, if you follow the Walstad method you should have enough cap of sand that catfish and plecos cannot dig it up. Perhaps a burrowing fish like loaches or gobies but your regular run in the mill fish should not have that much effect on the cap whatsoever.

I also don't believe that it is the bacteria you're wary of but the gas buildup. This only happens if the sand cap is too thick, this does not happen in gravel NPT's or rarely does it occur unless you literally have five inches of gravel cap to 1-2 inches of soil which just shouldn't be done in the first place lol But you can't avoid the anaerobic soil if you have a sand cap, except for by making it not as thick and using trumpet snails or poking the dirt each week.

I don't mean this as an argument, just to clear things up a bit hopefully. Take it as you will though.


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## rpadgett37 (Jan 1, 2014)

I was under the impression that anaerobic soil is not desirable in any soil based setup for a variety of reasons. I am new to this type of tank and have only read aabout them and asked questions. Please feel free to correct me on this point for my own education.


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## lilnaugrim (Mar 27, 2013)

You are right rpadgett, it can gas your fish and kill them which clearly, is not a good thing lol.

Did someone say it was beneficial? Did I miss something?


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## rpadgett37 (Jan 1, 2014)

No. Just wanted to clarify about anaerobic soil, that it can happen in any tank with soil other than a Walsted style setup, and is equally bad.


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## lilnaugrim (Mar 27, 2013)

Ah, gotcha, gotcha. Yeah, you're right


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