When we used the term “sand” we are referring to sand-sized grains (0.25 to 2.0 mm) composed of the mineral Silicon dioxide {SiO2), aka silica crystals, as being typical found in (sourced from) granite and quartz rock.
Criteria 1:
That the sand used “drains well” … and nearly completely. “Drains well” basically means going from a fully saturated (completely flooded) condition to when observable (unrestricted) drainage ceases within approximately 10 to 20 minutes from a 1/3 meter deep sand profile – once input pumping has stopped.
Drainage rate (aka hydraulic conductivity) is dominantly influenced by the average particle size but also by the specific particle size distributions (proportions). Smaller particles (the more of them there are and the smaller they are on average) will produce increased drainage times (slow the drainage rate). Also, the smaller the average particle size is the more water will be retained (not freely drain), which would then occupy more of the pore space (blocking O2 and therefore inhibit aerobic organisms which includes plant roots), especially in the lower portion of the depth profile.
Criteria 2:
That the sand is chemically inert, meaning that it does not significantly change the pH of water coming into contact with it.
In other words, it does not contain water soluble compounds (material), such as Calcium carbonate (CaCO3) or Calcium Oxide (CaO), as two common examples.
With a source water at pH 7 or below, a pH change of the water with each flooding/return of 0.0 would be ideal, but pH +0.1 to +0.3 under initial conditions may be acceptable. Remember than pH is a logarithmic scale, a change of one pH unit (+/-1.0) corresponds to a ten-fold change in the Hydrogen ion concentration.
NOTE: Use of source water above pH 7 is NOT advised. If your ground/source water is, for example, pH 8, then lower the pH (with an acid, i.e Phosphoric or Sulphuric) to below pH 7, BEFORE adding it to the system. In such a case, a separate (independent) storage tank expressly for this purpose is advised. Harvesting and use of rainwater is strongly recommended for virtually all locations.
Criteria 3:
That the sand contains NO contaminants such as heavy metals, radio-nucleotides, water-soluble salt(s), plant pathogens, or man-made chemical pollutants to include all pharmaceuticals.
Example metals and nucleotides include: Antimony, Arsenic, Cadmium, Cesium, Chromium, Lead, Mercury, Palladium, Platinum, Plutonium, Radium, Thorium, and Uranium isotopes.
These elements are found only EXTREMELY rarely (not a legitimate concern) in manufactured sand (crushed from ‘virgin’ granite or quartz) but MAY be found in certain natural sand deposits, particularly along river banks and lakes downstream or downwind of human/industrial activities.
Beach sand is almost always dominantly Calcium carbonate and therefor is not suitable (exception being volcanic glasses). Limestone is obviously not viable and neither are most sandstones and other sedimentary composites, unless exceptionally ‘pure’ (99% SiO2).
That’s it, folks: 1) drains well, 2) chemically inert, and 3) no toxic contaminates.
A final note of CAUTION: Do NOT accept any vendor’s claim of anything as being true (factual). Always test the sand source being considered (drainage rate and pH effects) for yourself. Minimize the risk of potential contaminants by sourcing ‘virgin’ crushed stone.
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Further information can be found at:
Hai…Mark…
Do iAVs Fish Tank Need A Rain Shelter Or A poly house…
I’m Running A system With Sand Beds Kept Under Rain Shelter(see through sheet).But The Fish Tank Left Opened…
Will It Make Any Negative Impact…
FT Will Over Flow When Raining…(Neutrients May Loss)…
Any Suggetions…
Entirely depends on how much rain you’re talking about. Certainly wouldn’t want the tank to flood (overflow) such that the fish can get out or for the entire system to flood. I can’t guess what the precipitation patterns are like were you are. I can say that it is generally preferable (wise) to take basic precautions rather than to accept preventable losses/risk. And, although I’m in an area that receives very little rainfall, I’d still cover/shade/protect a tank to 1) reduce evaporation losses, 2) reduce solar heating of the water, 3) suppress algae blooms, and 4) minimize intrusion by predators (here that would include osprey, eagles, hawks, fox, raccoon, otter, two bear and three feline species – and possibly an untrustworthy neighbor or three).
We have heavy rains here in india..
I already put a shade over the pond and rain will tickle through that…
Will this rain water make any change in water chemistry….
Perhaps, depends on amount and what the water chemistry was to begin with, Only way I can see to know is the track (record) what’s happening in/to your system.
Mark,
This is a very timely reminder…
I have ordered a county extension water test which will give me about 15 water parameters. My titration test and electronic tester both agree that our city water is really alkaline….to the tune of 9.5 pH.
More to come once I get the test results back from the county, hopefully by the end of the week.
Thanks……….mh
Personally, I wouldn’t knowingly bathe in pH 9.5 water, much less drink it, not to mention rear fish or attempt to grow plants with it. I do quite well harvesting rainwater at zero cost. Yeah, I filter it, and in the case of drinking water down to 0.2 micron with ceramic stones with Silver iodine cores ,,, ‘hardly necessary’ at all for iAVs (gardening). Even here, with all of 12″ of annual precipitation, my 1500 gal. household cistern has never fallen below 1/2 full with a mere 330 ft2 of catchment surface. My ‘fire dept’ cistern has 5000 ft2 of catchment and 25,000 gal capacity, is drained overwinter and filled between April and June. Just saying all this to provide some idea (context) for how much water one can collect from relatively low rainfall.
Getting my rainwater collection system together, have several site challenges to overcome, but should have something in play by the EOM.