I dug this post up from Buddha from 10/06...will copy and paste directly:
This was from a gentleman from Frognet... I though it was interesting... About silicon Soil
Hi George, John,
Thanks for the kind words about my silicone soil article from many years ago.
Here is the info that several of you have asked for. I have posted some of this in the past so some of this is old info, some of it is new.
In order to create a river that flows from one side of the tank to the other, I create a streambed out of what I call silicone soil.
Silicone soil is a method that I developed many years ago in order to create streambeds that solve a number of problems relating to water falls, stream / river bed features, etc. Its far easier then slabs of rock, rock chips, bark chips, Plexiglas, ABS / PVC pipe, PVC shower pan liner, etc. It produces a real nice natural stream flow. (Water doesnít instantly percolate down through the substrate leaving you with only a small trickle. Also you can use a smaller pump to get the same stream effect.)
The only drawback to the system as I have done it in the past is that I have used silicone caulking. While it is very cheap and is easy to get, it is also extremely sticky which makes it a bit difficult to work with. Because it wants to stick to everything it is not real easy to spread and smooth. There are ways to deal with the stickiness though, but it does take a bit of practice. Even with the stickiness, I feel that it is still far easier to get a natural looking waterproof stream bed using this process than using any of the other methods mentioned above.
Even so, I have been researching the possibility of using one of the mold making or makeup grade RTV-1 silicones rather than the caulk. They donít have nearly the stickiness issues and would be much easier to shape into the desired stream shape. RTV silicone can come in many different forms. I was going to experiment with the process but because of the health issues I have been dealing with, I havenít money nor ability to play with it at this time. I donít know whether the highly viscous form when mixed with soil would be entirely waterproof. If not, would adding thickeners or using the paste form be a best way to go. Anyone up to doing a little experimenting?
This too is a long post; sorry about that, Brent has learned, me Iím a little slow. Anyhow, a number of people have asked me to elaborate so here goes. If this is too long, at least check out the questions that I would like to see answered in the summary at the end.
The Process of Forming A Stream
You can use any base that you want. Personally I prefer to use some type of gravel base for the tank; this provides a great deal of filtration. Gravel does a better job than does a false bottom system because the gravel system provides a great deal more surface area for the good bacteria to grow thus providing more biological filtration. This type of filtration pulls out toxic wastes like nitrates. Thus you have to do a lot less maintenance, i.e. Water changes, less pruning, (plants grow a bit slower because there is not as much fertilizer around), etc. As for the types of gravel to use, I have two tanks with regular gravel (heavy but cheap), and one tank with cat litter. I use the cheapest cat litter available, one that is all clay. Avoid anything with deodorizers, clumping agents, etc., bioballs (light but expensive), LECA (also light but expensive), one interesting filtration *product being used in the aquarium trade, is the plastic wadding used in loading shot gun shells. (cheap and light). I havenít tried this last one. When I use something other than gravel I put gravel at every glass surface for the natural look. I also like the system I saw on Ken Uy Ďs web site, EQUIPMENT-Water System
which drilled the tank and put a second very small ancillary tank behind the tank, connected by bulk heads, one going out of the tank, one coming back in. This allows you to put the pump outside the tank where you can get to it for maintenance. You could also put an overflow drain from the second tank which keeps your water level consistent even when you are adding water from spraying, misting etc. It also makes water changes real easy. The ancillary tank is also where I would put a heater if I needed it. For the record, I have never had a tank heater in any of my tanks, but if you have up/ down thermostats that drop temperatures into the 50s or something, I would consider it. Many others use a false bottom system. Kenís site and many others can show this set up.
The Layout the Substrate
The first step in the process is to lay out the general terrain of the tank. The stream layout is sculpted in the gravel / soil substrate. I usually sculpt the substrate about 1/4Ē to 1/2Ē deeper then my final stream bed thickness. The soil used can be anything: Potting Soil, Atlanta BG mix, orchid mix, dirt from out side, cat litter (one of my favorites), anything. This was a soil mix that was posted on frognet a while ago.
The Home Depot Soil Mix:
1 part charcoal (available at HD for a lot less than the aquarium stuff and not quite as good, but more than sufficient)
3 parts milled sphagnum moss (this will look like peat)
2 parts small orchid bark (fir bark)
2 parts shredded coco mat (just buy one and take some scissors to it)
There are other recipes that can be found on the web as well.
The only thing I donít recommend is using any soil that has perilite, the stuff with little white styrofoam balls in it or anything with vermiculite in it. These products donít look natural and they can cause impaction if your animals ingest them.
If you are using dirt from outside, I would recommend that you sterilize it by baking or microwaving it and then letting it cool.
Making & Using Silicone Soil
Itís time to mix it up a little. Mix together the sterilized soil with any aquarium safe silicone. When I use silicone caulk I usually squirt a bunch of silicone onto on a piece of cardboard and then mix in the soil. RTV might make the mixing much easier, because it is so much more viscous than the caulk. RTV would need to be mixed in a throw away bowel though. Keep mixing until everything looks like wet / damp soil.
I use a Popsicle stick or plastic spoon to apply the mixture, sculpting from the waterfall down through the channel you created in the substrate until you get to the pond. You can use your fingers to shape, mold and smooth out the channel. You must wet your fingers often with water to keep the mixture from sticking to your hands. One note, whatever you apply this mixture to must be fairly dry as Silicone does not stick to wet surfaces.
You can add rocks at this time by pushing them into the mixture before it cures. Adding rocks breaks up the flow of the channel, creating little white water rapids, course changes etc., and it looks great.
The advantages of this system are numerous. The stream bed looks very natural, flowing around bends, rocks, branches, plants, etc. and keeps the water flow at the surface where it looks better, aerates the water, and adds to the tankís humidity. Plants that donít tolerate bog conditions can be put closer to the stream without rotting out because the water is held at the surface. The channel can be carried completely across the tank without losing much of the flow and without greatly increasing the size of your pump. Doing this also greatly increases the natural biological filtration in the tank, if you are using some type of a gravel bottom especially if you place the pump , or pump intake on the opposite side of the pond. You also wonít have nearly as many stagnant areas. The streambed can be cut out, altered and added to just by mixing more material. The streambed can be scrubbed to remove algae and it can be removed if needed, sterilized, and reinstalled. Finally, frogs and critters just love to sit in the stream.
The bed should cure in a dry environment for a minimum of 48 hours before adding water. Leave the lid off of the tank to let it cure and off gas. I would let it set for a week or more before adding animals. A week is probably overkill, but why take chances.
I didnít know this before I started researching, but most of the silicone we use actually requires moisture in the form of humidity in order to set or cure.
Limits & Problems
The mix does have some limits, If the mix has too much silicone and not enough soil, the end result looks too white and shiny. If the soil has too much moisture, the soil will tend to flake off after the silicone is dry, leaving a whitish, shiny area of silicone. Tinting the silicone or using colored silicone would help eliminate some of these issues. The mixing process is not super critical, or touchy though. Having a dry soil, bark dust, sand mix, whatever mixture you choose, is the key. Most potting soils and sand box sands that you buy are too moist when they first come out of the bag and do need some drying. Pop the soil into the oven to dry things out and let it cool before you start mixing can help get rid of the excess moisture and will therefore give you a much better looking final product.
Hope this is helpful.
Summary : Silicone RTV vs Silicone Caulk???
I know that Silicone Caulk does work for streams, but until you get used to it is a bit of a pain getting it into place. RTV may solve this and make waterproof streams easy as pie with everyone doing it. There are a lot of different types of RTV though. Which type would work the best? Would mold making RTV stick well enough to the rocks & gravel? It is, after all, designed to release and not stick to the original piece being molded on one hand, and on the other it is designed to stick to itself as well as to other types of silicone. If mold making RTV doesnít bond well enough, maybe using FX silicone, silicone used in make up and special effects work might be better. Would thinning down regular silicone caulk make it easier to work with? Or maybe mixing RTV with silicone caulk might do the trick. I donít know.
Tracy, with your expertise in Art world, have you worked with any of these products? Any suggestions?
Many of these products can be found in hobby shops and at art supply stores. Anyone up to a little experimenting???
Other uses for silicone soil
I use the silicone soil mixture for a number of other things as well, feeding dishes, plant pots, etc. I coat the outside of certain types of feeding dishes with the silicone soil so that the dish blends into the background and looks more natural. I also will use plastic cups cut down and sunk into the ground and glued into place with silicone soil for feeding dish holders. Then I will cut down another cup that will fit inside the first cup. The second cup will be used to put food into the tank. Works great for food like meal worms, etc. if you are doing reptiles Plus I can then pull the cup out and wash it when it is need.
I have used double pots to plant various plants in a number of different tanks while still maintaining a natural look. I found it worked best when I used two identical pots that fit snugly together. I installed one pot in the soil / gravel permanently and used the other to hold the plant. It made it easy to plant / remove plants. I donít tend to do this with my dart tanks, but it is a nice option it you want to try adding a bonsai plant which needs root pruning occasionally. I have used silicone soil to camouflage the permanent pot. It worked pretty well.
I donít pot most of my plants, but there are a couple of reasons that I do use a pot in a tank.
1. A pot will tend to contain the roots of a fast growing plant and a root bound plant will tend to grow slower so there is less time spent trying to manage a plant by pruning it back, etc. Some plants will over grow a tank in less than a month, crowding out and killing any other plant's chances of success.
2. I may also want to remove a plant periodically to prune it's roots or for shaping the plant's structure, etc. as when you work with a bonsai plant. I will place a pot in the tank that will hold the plant's position in the soil. Then I will pot the plant in a pot that nests and nestles down into the position holding pot.
I like my tanks to look as natural as possible, so any pot's surface that is exposed is likely to get the silicone soil treatment. This even includes the insides edges of the pot that houses the plant.
If you use plastic pots, make sure that you sand the pot with sand paper in order to roughen up the surface so that the surface has some tooth on which the silicone soil can grab onto.
There are times that the inside of the pot is exposed or the pot / plant that I want to use is deeper than the soil in the area that I want to use it, so I have applied the sticky mixture to the exposed insides & outsides of the pot. This camouflages the color of the pot so that it now blends and matches my soil. The rough blotchy soil mix now also camouflages the unnatural round flattened edges of the pot. Now rather than an exposed artifical pot, I have a little irregularly shaped hill, which the frogs can hide in and around as well.
For a bonsai plant that I put into one of my tanks, I built a pot out of that acrylic that matched the contours of the area where I wanted it. I then put silicone soil on the outside surfaces of the point and it sat looking very nice in its corner. This allowed me to contain and shape the roots so that they were visible and part of the display.
24 Auratus (B/BL; G/BL; B/Br; El Cope; Bnz; Camp) 5 Truncs, 4 Tincs (Patrica), 7 Vents, 5 Luecs (FS)
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