# Questions from Down Under about substrate and fish choice



## Bunbury (Oct 14, 2008)

Hi there

I'm new to NPTs, having just read and loved Ecology of the Planted Aquarium. The description of the aquarist who fails with plants and ends up discouraged before going 'high tech' really resonated with me! I'm keen to convert my four footer to an NPT, mainly to conserve water with fewer changes, but before I do so, I have a few questions.

This is going to sound dumb, but can someone describe to me what "potting soil" is like? Where I'm from we don't have "potting soil" per se, it's called "potting mix" and it does not contain any real soil - it is a mixture of (mostly) partly-composted bark and a little bit of river sand. Would this be suitable? Most potting mixes also contain a lot of water-holding crystals since we are constantly in drought. 

I've tried submerging garden soil in a bucket, to see what would happen, and ended up with an oil slick on the water surface. The slick is presumably from gum tree (eucalypt) oils - that's what it smells like, at any rate. Gum trees are poisonous, so I don't think that this would be safe even if I can get rid of the oil somehow.

I keep male fancy guppies in a show tank and some of the strains are weak, overbred little things. Are they likely to fall apart if I put them into an NPT?

Any ideas, thoughts, suggestions would be much appreciated.


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## Rusalka (Jun 11, 2008)

Hey there and congrats on switching to NPT! 

By garden soil do you mean dirt you dug up from your lawn or yard? If not - try it out. Some of the best soil for an NPT comes from right outside your house. If yes, then it does indeed sound like it wouldn't be a good choice for an NPT. Aside from being dangerous to your fish there is also a small possibility that the antimicrobial properties in the oil could mess with the natural bacteria in your tank. Maybe one of the other members could speculate if rinsing the soil might help? 

That potting soil you mentioned does sound a little strange - but it might work. I would try to get rid of as much of the bark as possible otherwise the major decomp might cause havoc when submerged. All soil is just a combo of sand and decaying organic matter anyway - yours is just much newer... That being said the kind of soil that would be best is one that is dark in colour, uniform in texture, with no added fertilizers or other chemicals, and with no tiny styrofoam balls (otherwise known as perlite). In North America that is often the cheapest soil you can buy, because there are no additives. It's basically the same as the soil you've got but at a further stage in decomp. Maybe you can sneak out to an organic farmers field and "borrow" a bucket full of their well used soil... haha.


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## cs_gardener (Apr 28, 2006)

Instead of potting soil I use top soil. The potting soil here either contains a large amount of wood chips or else it has fertilizer and other unwanted additives. Do you have any bagged top soil available? Not a top soil amendment but actual top soil. What you want is dirt and it's too bad that what you dug up had the oil in it. I don't know if that would be safe to use.

NPTs usually settle down in a month or two. At the start it would be a good idea to have your guppies in a different tank. After the tank has settled and ammonia, nitrate, and nitrate readings are acceptable you can add them in and they should be fine. I managed to shorten the time it took for my last tank to settle in by mineralizing the soil before I used it. This thread shows the mineralization process. It takes a bit of time but the lack of algae and ammonia spikes upon startup made it well worth it.


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## gravy9 (Aug 28, 2008)

Congratulations on going the NPT way.

I agree with Catherine. I used top soil for my NPT. It contains some organic matter along with dirt. The organic matter breaks down in the first 4-6 weeks and will leech into the water. This requires regular water changes until the leeching settles down. Once the leeching stops, you can go for a long time without changing the water.

I'm also working on the Mineralized Substrate method posted by Aaron as Catherine mentioned above. Should be ready in the next month.

As for getting a better idea on the types of soils, you can check out Scotts website.

Hope this helps. Good Luck.


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## Bunbury (Oct 14, 2008)

Thanks so much for all your help!!  Yes, by "garden soil" I did mean the stuff I dug up out of my backyard.

I'll buy some bagged topsoil from a landscaping supply shop and hopefully that will be reasonably free of any tree oils.

In the meantime I might do a few experiments with the potting mix in a bucket, before going to the trouble of setting up a tank with it.

Thanks again


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## gravy9 (Aug 28, 2008)

Looking forward to your test results. Please post your progress.


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## Bunbury (Oct 14, 2008)

Over the past few days I've been experimenting with plants in a couple of 20L (I think that's about 5 U.S. gallons) plastic containers - one with my newly-purchased topsoil and another with the aforementioned potting mix. In one, I used 4 cm (about 1.5") of the soil and topped it with about half that height of 5mm-diameter river gravel. In the other, I used 4cm of potting mix topped with the river gravel. The plants are Ludwigia, Elodea densa, Ambulia, Vallisneria and a small variety of Amazon Sword.

The topsoil I bought isn't really very convincing - it looks like they've bulked it up with manure, compost or maybe even the sludge you get when dredging rivers. It is generating A LOT of heat just sitting in the bag and even though I let it gas off overnight to remove some of the ammonia, I'm thinking there's far too much organic matter in it. 

The Ludwigia in the container with the topsoil went brown and disintegrated in just 48 hours, so I fished it out. Some of the Elodea leaves did the same thing, but it is already sprouting vigorous new growth from the stems, which are still in good condition. I didn't wash the river gravel and I think perhaps I should have - it contains some red silt which is probably iron oxide. Maybe there was too much iron for the Ludwigia. Or, if it was grown in cooler conditions before I bought it, it could have been too hot for it, since the temperature's up around 32C (about 90F) at the moment (though this doesn't bother any of my other plants).

The potting mix is doing surprisingly well - it didn't cloud the water and literally after only a few hours of sunlight the Elodea started sprouting new growth.

When do you think it is likely to become safe enough to add a few tough native fish to the containers? Since they're outside, they're going to become Mosquito Larvae Central unless there's something in there fairly soon.


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## gravy9 (Aug 28, 2008)

I would recommend that you keep monitoring the Ammonia, Nitrite and the Nitrate content in the tank. Once, you're in the safe range, I'd recommend starting off with some hardy fish. Wait a while until you put some sensitive fish in the tank.

I'm not recommending any specific fish as I'm not aware of what you already have and what is available close to you.

Good Luck.


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## dwalstad (Apr 14, 2006)

Bunbury said:


> The potting mix is doing surprisingly well - it didn't cloud the water and literally after only a few hours of sunlight the Elodea started sprouting new growth.
> 
> When do you think it is likely to become safe enough to add a few tough native fish to the containers? Since they're outside, they're going to become Mosquito Larvae Central unless there's something in there fairly soon.


The potting mix sounds like a winner. I suspect that almost any fish added to this container would do fine. Your fancy guppies may even do well with it!

I would dismantle the other containers. They're not worth your time (since you have found a good soil). Dying plants will pollute the water making it unsafe for fish. If plants are dying, you can be sure that the soil has major problems. Eucalyptus trees are famous for producing potent allelochemicals against other plants & trees. Allelochemicals could be what's killing your aquatic plants. If an eucalyptus-enriched soil was well-mineralized (that is, decomposed, composted, etc) the allelochemicals would also be decomposed and not cause problems. But decomposition takes time and vendors may be in a hurry. 

I'm impressed with your experimenting. Good luck!


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## Diana K (Dec 20, 2007)

The potting mix does sound like the way to go. If it has pieces of bark or other stuff that is large enough to identify I think I would sift that out, but leave the rest in there (sand, finer organic matter). 
If you want some kind of mosquito control in a relatively small bucket you might get some feeder guppies or some other small, durable fish. I would keep the test buckets in the shade, or else you will have boiled fish pretty fast.


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## Bunbury (Oct 14, 2008)

Thanks so much for the kind advice and help!  I really appreciate it

The Elodea has set itself on a course for world domination! The growth is nothing short of amazing, it has already filled the box and I'm thinning it out daily. The other plants are fine, but apart from the Elodea, only the Ambulia has shown much actual growth.

The other night I put a male pulcher kribensis in the box to clean up the population explosion in mosquito larvae. He had the time of his life - ate all of them in one night. He's now back in his usual tank, since I didn't want to leave him outside in the heat, but the mosquito problem is solved for a few days until I can get out for some blue-eyes (Pseudomugil signifer, native to this area).

If anyone is looking for a species that thrives in hot, hard, alkaline water, I'd thoroughly recommend P. signifer if you can get them. Our local creek is bone dry more often than it's got water in it, but whenever it rains, they appear. They're so adaptable they also live in the hinterland where the water is soft, cool and acidic, and people out towards the bay even find them in brackish and seawater.


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