Seeking info on dosing with tiny amounts of bleach

[seaslug]

For my M.S. thesis at UCSC Ocean Sciences, working in tanks at meso-scale, I'm investigating weak DC electrolysis for biological reef restoration.  A side reaction at the anode generates chlorine, which is of course a highly reactive oxidizing agent. However, I'm seeing indications that very diffuse molecules of resultant chlorine-containing compounds (including sodium hypochlorite) could actually provide an overall benefit to corals (i.e., at low enough levels, a differential effect whereby competing algae and bacteria, that are perhaps more susceptible, are suppressed without visibly harming corals).  Is any info available with regards to periodically injecting aquaria with minute amounts of bleach as a means of prophylaxis?  Something along the lines of a time-weighted safe level?  Insights greatly appreciated!

[devonjohnsgard]

Interesting...Following.

You are talking about Redox here. I'll try not get the waters muddy, by the moderate understanding I have on the subject. For what reason are you using bleach, when there are others, which affect Redox? Is it because of how strong the agent is? I believe it's going to be hard to find information on levels of beach in a aquarium. Most if not all people dont do this, so it would have to be a focused study a agency has already done. There is good information on Redox though, so I wonder if some connections can be made.

[Carl]

You mentions meso-scale aquariums (intermediate size); is there a specific size range you are working with; Example 60-100 gallon?

I have used bleach for plant dips where by the diluted bleach amounts were enough to kill the algae, but not the plant.

From my Plant Care article:
"Bleach used in a 20 parts water to 1 part bleach for 2-3 minutes for delicate plants and 4-5 minutes for broad leaf plants. Follow this with a quick dip in sodium thiosulfate, or another de-chlorinator/water mixture."
Reference:
www.americanaquariumproducts.com/AquariumPlants.html#other

The above said, I have not used small amounts of bleach/sodium hypochlorite for the benefit of coral.

I could certainly see where this might be beneficial for certain bacteria that might harm or out compete with the coral polyps for food. However with symbiotic zooanthellic algae I am unclear how this might be beneficial other than maybe acting as a "cleanse" since with Redox, we need both oxidation and reduction in varying degrees depending the particular aquarium environment in a snapshot of time.

I am certainly interested in any test result you do find

Carl

[seaslug]

I’m investigating claims that weak DC electrolysis is able to accelerate the growth of reef-building tropical corals (either mounted on or in the vicinity of the cathode) beyond natural rates. This technology (Biorock) has been deployed in the near-shore environment at many locations worldwide. I’ve downscaled circuits that fit in 2 meter long 1400 liter tanks, with the cathode located at the seawater inflow end and the anode at the outflow end. I noted that in relatively low water flow conditions, fouling algae, benthic diatoms and/or cyanobacteria appear to be suppressed when compared to the growths seen in an unpowered tank. In the powered tank, the growths are also lighter in color (as if bleached?) and take on a fluffy appearance, portions of which fall from the side walls (as if lysed). It’s well understood that some chlorine gas is produced as a side-reaction to how water is broken down at the anode, but (to the best of my knowledge) chlorine and resultant chlorine-containing compounds hadn’t previously been suggested as the source of a mode of action which could be potentially beneficial to corals in an electrolytic system. That is, in addition to effects attributable to how water is split at the surface of the cathode (including elevated pH and alkalinity, perhaps making it easier for corals to calcify, and/or the electric field possibly contributing to the gradient across corals’ external membranes that could reduce their enzymatic costs for pumping electrons and protons). It now seems plausible to me that, at the “right” concentration, molecules of chlorine-containing compounds (from chlorine produced at the anode) being diluted and circulated within the vicinity by waves and tide, could actually produce an overall competition-reducing positive effect (if it so happens that corals are relatively less susceptible to damage from bleach than certain fouling organisms).

[Carl]

These are interesting hypothesis.

I have found that Cyanobacteria in particular is more prevalent when water conditions and even more so lighting is less than optimum for the specimens we generally consider desirable in our aquariums.

It’s well understood that some chlorine gas is produced as a side-reaction to how water is broken down at the anode, but (to the best of my knowledge) chlorine and resultant chlorine-containing compounds hadn’t previously been suggested as the source of a mode of action which could be potentially beneficial to corals in an electrolytic system.
That is, in addition to effects attributable to how water is split at the surface of the cathode (including elevated pH and alkalinity, perhaps making it easier for corals to calcify, and/or the electric field possibly contributing to the gradient across corals’ external membranes that could reduce their enzymatic costs for pumping electrons and protons).

My question would be whether the chlorine gas is measured at any distance from the anode and what its lifespan is in a well circulated, established, healthy aquarium with correct chemistry?

I ask this as maybe the reverse is happening in that while chlorine gas is being produced, its lifespan is very short (which has been my experience with small does of chlorine introduction into a healthy aquarium), and possibly you are observing some Redox Reduction benefits from the electrolysis. I ask this question because higher life forms seem to benefit from higher reduction within their cells, whether coral polyps fall within this, I do not know for sure.

Carl

[seaslug]

Thanks for your insights. This is precisely the area of inquiry: whether weak DC electrolysis does indeed provide a benefit to corals, and if so, how much and by which process(es).