lduncan

KH plays a pH buffering role. A buffer is a substance which resists the change in pH around it's natural pH level. The higher the KH, the closer the pH will be to 8.3ish, and the more it will resist any change in pH around this value. Peat is full of weak organic acids which can also act as buffers, but are centered around a lower pH, and will resist changes in pH around a lower pH than what KH does. Layton

Sounds good to me. Just a semantics thing, but alcohol is technically a nutrient for bacteria. It just happens that it isn't as an effective source for algae (including zooxanthellae), unlike nitrate and phosphate. Just the same as the second part of the zeovit theory. Vinegar would be an interesting alternative to test too. Acetate (vinegar) is a carbon source which is written about a lot with respect to bacteria. Layton

Chemistry was my best subject... can't remember anything too advanced, just the basics now.

That explains the coralline.

Maybe the same way corals do. Running a "high" pH may do it. It can be done. There is more of a link between calcium and magnesium levels though. A 4 dKH drop in a week isn't that much. Mine uses around that amount daily. From the calculations earlier, calcium carbonate is already supersaturated in sea water, so is prone to precipitating out at any time. Magnesium and phosphorous inhibit it by poisoning carbonate crystals to avoid a catastrophic chain reaction occurring. Of course the higher the calcium and alkalinity levels, the higher probability that these inhibitors can't keep up with their poisoning, and result in precipitation being easier to trigger. Equations don't really show much when the solution is supersaturated as it is in seawater. It is possible to maintain both high alk and high calcium, but it does make catastrophic precipitation easier to trigger. Jes, I don't post for a few hours and someone get suspecious . Just too busy working . Got to pay for the house some how, especially after not working (for money) as uni was taking up my life for the last 6 months or so. Layton

... and CO2 levels.

That may do it. But it will more than likely take many many months. Unfortunately that won't prove that there is no ich in your tank. All it will mean is that the powder blue didn't noticeably contract it. I've added a powder blue to my tank, it never had any outbreak of ich, but I know ich is in my tank. That's what i mean by it not being a problem with calm and happy fish. Dump a lot of fish into a new environment quickly, and your going to have problems. Layton

... depending on atmospheric CO2 levels around the tank. Layton

So a percentage of fish become immune after exposure. There is going to be a definite probability that a fish will become infected again. And only a percentage of viable theronts are going to find a host to complete the cycle, lets say 10% just for arguments sake. Of course the viablility is dependant on how long it takes for them to find a host. So the stats game is where the theronts have fewer and fewer hosts to infect due to immunity, so the theronts stay in that stage longer, which increases the probability of them dying from not finding a host. This will slowly diminish there numbers over a longish period. Definitely not a quick fix. Plus you can really never know if it is still in your tank or not. A fish can have a minor infection without you knowing. It's hard to spot a few cells with your eye alone.

Well there are two ways carbonate sand can dissolve. Purely chemically, or alternatively with the aid of bacteria. And the bacteria don't do it just for the fun of it. They use it, meaning other animals in the tank don't get it in the form of alkalinity. So I think sand has little if any effect on buffering the water against pH changes. Layton

so you're going to ? Layton

Those equation are reasonably complex to solve so just looking at the dominant process: a0 = [H2CO3] / Fa = [H30+]^2 / { [H30+]^2 + K(a1)[H30+] + K(a1)K(a2) } a1 = [HCO3-] / Fa = K(a1)[H30+] / { [H30+]^2 + K(a1)[H30+] + K(a1)K(a2) } a2 = [CO3-2] / Fa = K(a1)K(a2) / { [H30+]^2 + K(a1)[H30+] + K(a1)K(a2) } (It's damn hard writing equations in ASCII !) So then: CaCO3 (s) initial: solid change: -x final: solid Ca+2 (aq) initial: 0 change: +x final: x CO3-2 (aq) initial: 0 change: +x final: x So basically for x moles of CaCO3 dissolved, x moles of Ca+2 and x moles of CO3-2 are produced. But CO3-2 also exists as HCO3-. These are still related through K = [Ca+2](a2)(Fa) From the list above: K = (a2)(x^2) = 6 x 10^(-9) x = sqrt{ 6 x 10^(-9) / a2} where a2 = [CO3-2] / Fa = K(a1)K(a2) / { [H30+]^2 + K(a1)[H30+] + K(a1)K(a2) } and [H3O+] = 10^(-pH) Eg: for a pH of 8: [H3O+] = 10^(-8 ) a2 = 4.45 x 10^(-7) x 4.69 x 10^(-11) / { 10^-16 + 4.45 x 10^(-7) x 10^(-8 ) + 4.45 x 10^(-7) x 4.69 x 10^(-11)} = 4.57 x 10^(-3) x = sqrt { 6 x 10^(-9) / 4.57 x 10^(-3)} = 0.0011 mol / L So solubility at pH 8 is 0.0011 mol / L == 91 ppm Eg for a pH of 8.3: [H3O+] = 10^(-8.3) a2 = 0.009168 x= sqrt{0.000000654} = 0.00081 mol / L So solubility at pH 8.3 is around 67 ppm Remembering that a alkalinity of 10 dKH (around 3.5 meq/L) is equivalent to 178 ppm. Layton

First we need to consider the relationship between carbonate (CO3-2), hydrogen carbonate (HCO3-), carbon dioxide (CO2) and water (H2O). It's also important to consider phases: (s) = solid (aq) = aqueous (dissolved) (g) = gas The following chemical equilibrium are in process: Dissociation of sand: CaCO3 (s) <-----> Ca+2 (aq) + CO3-2 (aq) Water dissociation: H20 <----> H+ + OH- Carbonate / Hydrogen carbonate equilibrium: H+ (aq) + CO3-2 (aq) <----> HCO3- (aq) Atmospheric / dissolved CO2 relationship CO2 (g) <----> CO2 (aq) CO2(aq) + H2O <----> H2CO3 (aq) Dissociation of Carbonic acid: H2CO3 (aq) <----> H+ (aq) + HCO3- (aq) Equilibrium Equations Solubility Product of calcium carbonate: K = [Ca+2][CO3-2] = 6 x 10^(-9) Dissolved CO2: [CO2 (aq)] = K(CO2)P(CO2) where K(CO2) = 2 x 10^(-3) Water: K(w) = [H+][OH-] = 10^(-14) Hydrogen carbonate / carbonic acid equilibrium: K(a1) = [H+][HCO3-] / [H2CO3] = 4.45 x 10^(-7) Hydrogen carbonate / carbonic acid equilibrium: K(a2) = [H+][CO3-2] / [HCO3-] = 4.69 x 10^(-11)

Or confuse people I'll give it a go. I'll do it over a series of posts here: http://www.fnzas.org.nz/fishroom/viewto ... 738#106738

Someone requested my reasoning behind why i think that carbonate sands are limited in there ability to add to the buffering capacity of tanks. So i'll post the maths chemistry and assumptions behind this in this thread.

Well all life on earth is carbon based. Just so happens that alkalinity is the largest source of carbon in our tanks. It's kind of like asking for more info on why plants are huge consumers of CO2. quick google search comes up with this: http://www.sigmaaldrich.com/Brands/Fluk ... ology.html amazing the stuff you can find if you look If anyone wants I can run through the maths of the chemistry behind the carbonate sand not providing any significant buffering capacity. It'll take a few pages though. Layton

Warren, I couriered some off this morning, they should arrive Tuesday morning all going well. Had to get exams out of the way before I got organised with these, so they were last minute. Hopefully they arrive before your deadline. Layton

Yes to a limited extent. The extent is dependant on the cleanliness of the water (and sand if any), whereas the amount stored in sand is independent of water quality. All due to gravity and bacterial turgor. So if your rock is in clean water and sand, it will be storing minimal crap. It should be enough. Tank bioload using this method is mainly determined by your skimmers ability to remove crap before it breaks down. No it wouldn't store crap, but then it wouldn't have any benefits either, it won't be performing denitrification or looking good.

Well when you remove all the sand, you no longer have a sponge absorbing nutrients, so you can't afford to let detritus sit and rot in the tank, otherwise you will get phosphate and nitrate accumulation. It needs to be removed asap. If you don't have plenty of flow to keep it in suspension until it is skimmed out, be prepared to be siphoning relatively often. You've got a good skimmer, so as long as your flow is good, then it should be low maintenance. Layton

How?

Where has this been proven, any numbers for those claims?

I'd agree with that Ira. Ghostface: If the sand is performing denitrification then it will be storing phosphate and metals etc. pH stability isn't really determined or helped to any large extent by the sand. It's determined by alkalinity and atmospheric CO2 levels. I don't have any references as such for this, but my reasoning for sand not being as significant buffer as some think is the following. From a chemistry standpoint, the solubility of calcium carbonate in water at a pH of 8.3 is around 25 ppm, at a pH of 8 it is close to 75ppm. In terms of alkalinity (which is what the calcium carbonate sand turns into) a dkH of 10 (3.5meq/L) corresponds to a calcium carbonate concentration of 178 ppm So the calculated solubility of calcium carbonate at normal tank pH is 25ppm, this isn't taking into account the common ion effect (which can significantly reduce the solubility due to the presence of a common ion which may already exist in solution) this is well above the concentration which already exists in solution (178 ppm) which means that bugger all is going to dissolve chemically. The reason why the sand eventually does dissolve, is because bacteria create acidic micro environments which react with the carbonate to liberate the carbon they need to live and reproduce. Of course bacteria aren't perfect, and they leak, just like algae, so small amounts may make it into the water column. But the majority of this will be used by the bacteria themselves, otherwise they wouldn't go to the effort of creating these micro environments. Bacteria are a huge consumers of alkalinity. The bacterial activity in sand beds means that they can be significant consumer of alkalinity. If anything ditching sand can result in a drop in alkalinity demand, and therefore less chance you may need a calcium reactor. Depending on what you are keeping, you may not need a calcium reactor. Kalk may be adequate. To me the only positive effects I can think of from having sand is aesthetics, and nitrate removal. So I'd get rid of it altogether if you want to go the BB route. Layton

I remember reading that the difference in osmotic pressure it too much for these single cell parasites, an they either shrivel up, or explode, if moved from one environment to another. Layton

Good luck finding a tank which doesn't carry it. In my experience calm healthy fish don't die from ich. It is very difficult to eradicate ich completely. You can either kill it using copper or play a stats game and wait months or years until it erradicates itself through gradual fish immunity and death during the theront stage from not finding a host to infect.

Aragonite is limited in it's buffering abilities to the point of being insignificant. People think it is significant mainly because bacteria dissolve it within their micro environments as a source of carbon, this doesn't get released to the tank as carbonate alkalinity, it's consumed by the bacteria which liberate it. Personally I'd flag it altogether. Layton