Help on substrates to use for carpeted, planted tank hosting live bearers

jonatheber

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I am switching over to aquascaping from a standard gravel bottom. I have a high-tech 46g bowfront tank (other than the substrate) - Fluval 3.0 light, CO@ etc. My tank will have live bearers (mollies, guppies, cory cats, some tetras and a kuhli loach) My water runs high pH (around 7.8) and would love to get it to 7.4 or so, but not lower, if minimal changes from soil are possible. My tank is fully cycled at this point and I do weekly (most of the time) 40% water changes so the other balances are pretty good. For good or bad, I am not particularly cost sensitive - I have dumped so much into the CO2 (Co2art regulator, new tank, good light) that a few extra dollars on the RIGHT substrate is fine.

I definitely want tank to have taller plants in the back, with a full carpet and some smaller plants in the middle and front. If I do this right, the tall plants will hopefully be able to be easy and complicated - I'm hoping to get some colorful plants ultimately and those all seem to need to have deep roots. I am also VERY worried about all of the commentary about how aqua soils in general can cause the kH and pH to drop, and my fish need at least some minerals in the water and need a pH around 7.4 or so.

I am horribly confused by the different opinions here on the forums so I am going to through my current thoughts out there. I am thinking to put in three layers. The depths below are the first number at the front of the tank, the last number at the back.

Level 1) 1"-2" of Eco-complete - I figure this can't hurt. There will be water going through that base, there will be a place for bacteria to grow. As the soil (#2 below) starts to turn to mud, that mud will be able to sink down instead of sitting and fill in the spaces in the eco-complete. Not sure the last part will work, but it seems logical. I know some people think it is pointless, but unless it will hurt I don't see a reason not to do it. If nothing else, it is cheaper than the soil I'll use next

Level 2) 1"-2" of aqua soil only - while ADA Amazonia soil is very popular, I am really concerned that the ammonia won't be controllable for a while. My priorities here are to have a good growing medium for plants that root deeply and give off nutrients to help with growth up front, but try to find a soil that won't mess up the chemistry (guppies won't like pH that is TOO low) and won't degrade quickly. I can move my fish to a quarantine tank for a bit, but they won't last all that long because the 10g isn't really suitable for 15 fish for that long. I therefore wonder if something more neutral would be better that would lower pH slightly but not give off so much ammonia. Happy to get recommendations (e.g. Landen, Composoil (although I think that supposedly breaks down quicker)

Level 3) 1"-2" MIX of ADA and something inert but not too small like Seachem Flourite (happy for recommendations of something black here too). I don't want to do a full cap or sand because I have babies in the tank and bottom feeders and don't want them impacted. I also figure that mixing something intert with the soil will help keep the top layer more porous when it starts to degrade. I really want some soil up top - some of the plants don't have deep roots, and I have gathered from what HAS been posted that the carpet will grow much better if planted in good soil than just something inert. Doing the WHOLE tank with root tabs if I used something inert to encourage the carpet and more challenging plants in the whole bottom of the 46 gallon tank will be a royal PITA so I'd rather not have to worry about it.

This is my idea. PLEASE let me know where I'm off - I'm not stubborn. I'm just trying to find a happy medium between good for plants AND safe for smallish live bearers and bottom feeders, combined with a place that will grow the significant number of plants I want to put in quickly.
 

Essjay

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I'll let other members deal with the plant and substrate aspect, but there are problems with the fish list, I'm afraid. You have a mix of hard and soft water fish. Mollies must have very hard water, guppies can tolerate middling hardness but the other fish are soft water. There is no happy medium I'm afraid.

Can you find out the hardness of your tap water? If you are on mains water your water provider's website should have that information. Then you can choose fish suited to your water
 

WhistlingBadger

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I agree with Essjay about hardness.

As for soil, I think your plan is reasonably sound but overcomplicated. In all of my tanks, I do 1-2" of organic potting soil (make sure it's organic with no pearlite, manure, or chemical fertilizers) capped by 2" of sand. This kind of substrate will cycle your tank (the soil releases some ammonia as its microbes convert from a terrestrial to an aquatic community). This is a good thing unless you already have fish, which it seems that you do. (?)

If you already have fish and don't want your tank to establish a new cycle, I advise just using about 2-3" of sand, and add root tabs for your rooted plants. Well-rinsed play sand from the hardware store is the natural-colored substrate of choice for many on this forum, including me.

If you want a black substrate, the safest and most convenient option is to fork out the money for one of the commercial aquarium sands--they come in about any color you could possibly want, and a few you probably don't. :lol: You could also use black blasting sand (black diamond or similar) which is cheap and widely available. Some say this is unsafe for bottom feeders, and their opinion is worth taking seriously, but I have personally had good luck with it. @Byron and I argue about this about once a year or so. :lol:
 

Byron

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Several years ago I did research on soil substrates. I joined Diana Walstad's forum (she sort of pioneered this concept) and read her book and as many articles by her and other authors as I could. In the end, I decided it simply was not worth the risk to the fish. That does not mean it will not work; but it does mean it is not necessary for a fish tank that has live plants. And that is the primary issue here--the fish. You cannot have substrate-digging fish like the Botia loach species, and some of the loricariids like many plecostomus--I had a 4-inch Hypostomus furunculus that more than once decided to make a new home and he dug through and shifted 4 inches of sand down to the bottom glass under a chunk of wood. Corydoras should never be kept over any substrate other than inert sand; the bacterial issues associated with plant substrates, as well in some cases as the mess, are paramount.

As for the plants, there is really only one benefit to soil, which Diana herself admits, and that is the initial release of CO2 from the decomposition of organics. With a new sand or gravel substrate, it takes a bit of time for the organic matter to reach this state--but this is minor when one considers the risks. The other thing is that soil substrates have about a one year life, after which they no longer provide any nutrients that one cannot get with the inert sand or gravel. And, the general consensus among the planted tank authorities is having a dry start and no fish for up to six months (this is primarily the ammonia issue). There can be significant algae issues too.

Aquatic plants will grow well in almost any substrate. The grain size is the only actual factor that may thwart the plants, not the nutrients or supposed lack thereof. I used Flourite in one of my tanks for two years, and then got rid of it. I could not keep cories, and the plants in my estimation were no better than they were with sand. I still had to use fertilizers. Admittedly this is not the same as soil, but the point is that with fish present, it is probably better to forget soil.
 

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