Marine Discussion: Water Chemistry

Typopgraphic comments, both #3:

"conjugate" not "bonjugate" Corrected. OG

bidirectional arrows I do by <-> , i.e., dash rather than equation mark. It does not align well, but without a scientific font I prefer it. Not making this change, would rather get a concensus with the Happychem. OG

Great posts! I wish my chem teachers were this good in high school Or maybe I'm paying attention this time hehe. I'm curious what the next chapter will be...

Asking for clarification: Does the adsorption rate gradually decline, or is it an on/off situation? For example, if zeolite is used, will the adsorption taper off, allowing some ammonia to become available for bacteria, or will the zeolite work at the same rate until it's full?

It's difficult to quantify without knowing the available adsoption of the zeolite (which would probably be expressed in moles of NH3) and the NH3 production of your tank.

If there's some adsorptive capability remaining, it should grab the NH3, so I believe that it would have a pretty steep drop in activity. Nothing is really on/off, there's always some rate of change.

I believe that the drop in activity would be pretty fast because the adsoptive capability of the amount of zeolite added to a filter is likely to be a great deal higher than the amount of NH3 produced in a day. In other words, initially, everything would be snatched up, and fractions of the zeolite would be filled each day. Eventually there would be a fraction remaining that would be close to the amount of NH3 being produced, so one day it may take it all up, the next there may be a little to show, but the third you'd have the full amount being produced free.

Think of it like filling a cooler with brownies. Every day, someone gives you a brownie and you have to put it in the cooler or eat it. Let's make them poison brownies . At first, you have no trouble fitting them in, but after a while, there's room for one and a half. The next day, you break a brownie in half, but you have to eat the remaining half.

Yes, nitrifiers will pick up when this final stage is reached, but I think that the zeolite will fail at a much faster rate than the bacteria can grow to match. Plus the ammonia nitrifiers are limited by the zeolite adsorption in much the same way as NO2 nitrifiers are normally limited by NH3 nitrifiers, so there's another level of restriction placed on nitrifier growth, which I think will be more detrimental to NO2 levels in the tank that NH3, since NH3 nitrifiers can grow more quickly.

But, as I said at the beginning, without some kinetics experiments, this is all just an educated guess.

Something to consider with bio-media, specifically sinstered glass and other porous materials. Bacteria colonize internally but as the colony grows and some bacteria die off, they subsequently plug the small spaces and starve any remaining internal bacteria. Eventually, you end up with media that is only good for bacterial colonization on the outside. Plus, you have another source of decomposing matter, the bacteria within the media.

Actually there is anerobic bacteria in aquariums that do break down NO3 into nitrogen, so a complete cycle does happen. Since they live in low Oxygen enviornments they take the Oxygen out of NO3 and convert it to Nitrogen gas.

Biomedia in FW tanks are generally considered to be for the nitrogenous-waste oxidizers, which are aerobic. And the massive surface area claimed by that type of media is just about as meaningful as the massive surface area of activated carbon - as soon as any biofilm develops, the available surface drops precipitously, and you end up with an expensive rock, the equavalent of a piece of gravel.

If you want anaerobic reduction of nitrates (and the question there is really "Why?"), then there are alternate techniques for that which do not rely on the degrdation of aerobic biomedia to do so.

you mentioned moles a few times but never said how much it is. so in case ppl wanna know.. 6.02 X 10^23, known as avagadro's number.

so if pH is 1, then the concentration of H+ is 0.1 mole/ litre, or 60200000000000000000000 atoms in 1 litre. concentration of 1mole/L (M) gives a pH of 0. 2M gives negative pH! donno why im mentioning this.. i feel like i wanna let ppl know i know some stuff about chem.. which i think why most ppl post.

I did consider it, but the actual magnitude seemed unimportant, or worse, possibly confusing. A deeper knowledge of chemistry does require familiarity with Avagadros number, but unless you're getting into Quantum Chemistry, or some of the trickier Phys. Chem, the number itself becomes less relevant. It's like saying that there are 1,000,000 microns in one metre, if most of what you're measuring or discussing is best described in the scale of kilometres or metres, then talking about the number of microns just adds confusion.

One of the beautiful things about molarity is that it provides a scale for talking about the activity of molecules on a more macroscopic scale. Combining it with the metric system's unit designations: nano-, micro-, milli-, etc. add yet more power to it. The smaller the number used to quantify, the easier to understand and discuss. For example, we know that nanomolar (0.000000001 moles/litre of solvent) is a tiny concentration, but if that's the concentration range of our compound of interest then it's much easier and comprehensive to discuss it in terms of how many nanomoles are present. We clear out the zeros, figure out the chemistry and let our brain remember that we're dealing with very small numbers.

pH is a little trickier because it is an exponential base number sytem instead of a simple base 10 like we're more accustomed to. But as long as we keep in mind that a change of 1pH is actually an order of magnitude change then we're fine.

Besides, no aquarium is going to encounter pH 1 conditions, and negative pH isn't possible in an aqueous system, so keeping my discussion somewhat relevant to the hobby was part of my discussion. So, just finish your Intro. to Inorganic Chem.?