Okay, brace yourself. This is a response to your first post only!
Too many questions too fast! I am limited in on-line time, both by the board program and by my eyes. This is going to take a while.
1.
“From Pufferpedia:
Water Parameters: Low-end brackish water (SG = 1.005 - 1.008)”
My first issue with common practices is in the quote above. I never operate any tank at 1.008 other than briefly while increasing salinity. 1.008 is too close to the transition point for nitrification bacteria. I do not trust myself enough to ensure specific gravity within one unit, and certainly would never suggest it to anyone, especially a novice or any non-scientist without well-calibrated refractometers. It is too easy to slip over the line into the range where FW nitrification bacteria are being replaced by SW bugs. Most hobby measures are just not sufficiently accurate to risk operation at that scale.
2.
"Marine mix at 1.003-1.005 specific gravity does not provide enough alkalinity to keep the tank stable with sufficient alkalinity."
I use my tap water (source water) for low-end BW make-up. That water in moderately alkaline (KH 7-9, with seasonal variation from summer supplement with near-surface water. The deep aquifer which provides most of the water is quite stable. Thus my light or low-end BW does have more alkalinity (carbonate/bicarbonate hardness) than the mix alone would provide in high-rejection RO or RODI water. Others mixtures may well provide less or more alkalinity than mine, varying with the alkalinity of the water they use to prepare the low-end BW. The initial trials of the work I did to study the captive lifespan of F-8s in varied water conditions did show marked declines in KH during the week post water change (50% weekly). Plus, the effect was detectably\y different between FW and the various low-end BW concentrations tested. That introduced another variable, with greater variability in residual alkalinity during the week. Having two strong variables requires higher numbers of tests for clarity, so is undesirable. I put the study on hold and played instead with ways to help sustain the alkalinity. Frequent manual additions are laborious and carry some risks. Using aragonite substrate (aragonite is the most soluble of the three substrate types offering bicarbonate/carbonate make-up, so was selected.
I used Caribsea aragonite substrates. One-half to one one-inch layers did help sustain the alkalinity. RFUG filtration helped more than conventional substrate without flow-through, and OE-RFUG helped best, but the differences between the last two types was not large or significant without running as many tests again at least. As OR-RFUG ensured me trouble-free oxidation of ammonia to nitrate, that was the system chosen for the whole test series (without the use of much extra equipment, no alternate biofiltration required, killing two birds with one stone). The alkalinity did decrease in a week, but a lot less. Aragonite is soluble at pH well below that of the other readily available substrate form, crushed coral, and in small-scale trials did show much better replenishing of alkalinity to replace that lost in nitrification of ammonia to nitrite to nitrate. The test animals here were mature F-8s, all in 15 gallon tanks.
3.
“They are also obviously referring to SW, not light/low BW, which is an entirely different biochemical system and has quite different upkeep requirements.”
Yes, definitely. Low-end BW is more akin to FW than to full marine conditions. It is neither in actuality, but is closer to FW in handling and biology.
4.
“Here much (but not all?) of the bacterial component is identical to FW tanks, and nitrification is filter-based.”
Again yes, but also yes to not all. FW and SW bacteria are commonly not, repeat not, found only in ”their” type water condition. Mixtures are widespread and common, and not only in direct contact with the other condition in the wild. There are many, many techniques of bacterial transport. Mixtures of species from these two water types are expected. Even the oddball types which have no resting phase (as with FW nitrification bacteria) still manage to show up in the other non-favored condition. They may not thrive there, but may hold on to existence for some unspecified time period. Types with storage/non-metabolizing forms may persist indefinitely in small numbers.
Few hobbyists realize how many species of bacteria and infusoria and small inverts inhabit their tanks, and actually contribute to the stability of hobby tanks. Folks tend to concentrate on the generally but not exclusively filter-base bacteria which are required to sustain fish in the presence of un-oxidized nitrogenous wastes, but all the other bugs are equally if not immediately important. There are huge differences in immature tanks, and multiple issues which can arise during the first six months to a year. But well maintained tanks over one year old tend to be stable indefinitely, with some increases in upkeep and partials as the livestock itself matures. Balance is everything, and not many tanks balance quickly. But with a little help, they almost all do eventually if properly set and maintained.
5.
“If this is the case and the depletion of alk, is much higher than in regular FW tanks, does that mean there is SW bacteria in there also? If not, why are we not seeing this phenomena in FW tanks? If SW bacteria is present can we neglect the Ca/ Mg and Alk triangle to aid in the stabilization of the tank?”
I do hope that I never said that depletion of alkalinity is higher in low-end BW than in FW, or in SW. The rate of utilization in any of the three conditions of the alkalinity is directly linked and balances the nitrification rate of unutilized nitrogenous wastes. It is the same old chem.-speak “two milliequivalents of bicarbonate are consumed for every milli-equivalent of ammonia oxidized to nitrate”. The water condition matters not, the same chemistry occurs, just practiced by different strains of bacteria.
We see this phenomenon in FW tanks all the time. The untrained get suckered in constantly by the chains, web-merchants and even the LFS into buying chemical buffers (commonly phosphate based) which royally mess up the tank’s precariously balanced biochemistry and can even damage the fish while starving the nitrification bugs of the bicarbonate they absolutely must have to function. Folks with moderate alkalinity in their source water can use that water for low-end BW and help but not cure the problem. Too many of them use high-rejection RO or RODI – as already said – and magnify the problem. Folks with extremely alkaline water – we had one currently on the board who was given very bad advice on handling his low-end BW, and from a staff member here – may or may not want or even be able to use his high pH water for low-end BW. High hardness and alkalinity water is iffy for mixing with marine mix. It can be quite dangerous to livestock due to incompatibilities between the mix and the water. The reactions which can occur are similar to those in brine evaporation ponds, where the end product is incapable of supporting life.
Ca/Mg and carbonate/bicarbonate are, in solution, fully independent of each other. The bacteria involved in nitrification in filters we know now better all the time. In LR we have little info. But the SW bugs are unlikely to be primary at low-end BW, and we do know the transition zone between the FW and SW forms. However, it is likely subject to some shifts depending on the particular water profile. The heterotrophic bugs we really don’t know beans about. Particular groups may have transition points or ranges like the nitrification bugs, or may be simply directly variable with the salinity – although that is not very likely. Mid-to-high specific gravity is not very well known. It is pretty much a fog from FW nitrification range up to full marine. Then you can fight over the definition of full marine.
Pragmatically, your discussion of SW forms in FW is fully valid (even though I did not recopy it here). We only get to look closely at the nitrification bugs, because we can read their effects so easily. When we move slowly up from FW through BW to full marine, if we slow down and take 2-3 weeks to get through the transition range, we generally have no problems. Think about that in relation to normal tank cycling in FW or SW. Since that just happens to be the proper period for FW (or SW) fishless cycling, there is a justification for considering that there is at least an adequate inoculum of the SW forms present. Plus there is the cushion of the other type being still present in sufficient numbers to still handle part of the bioload, Even if they cannot continue to multiply as easily as in their own water type.
6. “
Pufferpedia states:
Minimum Tank Size: 15 US Gallons (50 liters)…"
Please do remember that ‘minimum” means just that, minimum. This is not, repeat not, “optimum” or ideal. Minimum is the smallest tank to hold as single specimen of the fish under discussion and nothing else, period.
7.
“Does that include a reverse flow, under gravel filter WITH aragonite?
This issue and its solution are unique to high bioload low salinity systems".
No, it means just and only minimum tank size and whatever the actual water volume is in that nominal size tank. If it had included RFUG or OE-RFUG with aragonite it would have so specified. The F-8 trials were still in process when that was written.
And yes, the RF w/aragonite is unique to exactly those conditions and that situation: High bioload fish with low specific gravity and low to moderate alkalinity which results in less than stable conditions between water changes. That does not limit the stock to this size tank or even to puffers, but to any high bioload fish in appropriately sized tanks which are to be maintained long-term in low salinity water.
8.
“Assuming that one is not using aragonite and a reverse flow under gravel filter (as it is not mentioned in Pufferpedia), one would assume that an F8 would produce 2.85ppm (not sure if ppm is the right measurement to use) of Nitrite per day at 15 gallons, given a 50% water change weekly. That is a pretty big bioload, but I know that swimming space is also factored in there.
If one is using aragonite and a RFUGF, does that change the tank requirements?”
No, it does not. Tank size of two feet long is not exactly optimum swimming space IMHO. Rather the opposite. I ran my F-8 trials in 15s, but I don’t keep and would not again keep pet F-8s in less than a 20-long and would prefer a 30 or 33XL myself. We are talking about a 15-year fish for goodness sake! That of course is personal, not what I say to every one of the forums. But I would not suggest less than a 20-long for one f-8.
9.
“When mentioned that high bioload and low salinity systems are unique, I wonder how so? It brings me back to the original question about shared bacteria and that maybe we should be testing for more than ammonia, nitrite, nitrate, and start adding portions of a marine system as well (alk, calcium and magnesium) to satisfy both strains of bacteria.”
Please do not confuse low-end BW with marine systems. They are apples and oranges, not at all the same thing. The bacteria have nothing, repeat, nothing specifically to do with the low-end BW need for alkalinity support. Normal nitrification can hit any low-alkalinity water condition hard, and a system crash is possible if the alkalinity is exhausted. It is unlikely to crash in full marine even if filter-based nitrification is used, but it is possible if the keeper will not do the required water partials. That applies to FW tanks as well as BW tanks – or to any filter-based nitrification system. Full marine is not best operated with filter-based nitrification. If operated with LR and a good skimmer and a macroalgae refugium, a full marine system may need regular supplements but not nearly such large water partials as filter-based nitrification. Smaller water changes are all that is required. That is, over the life of the tank, a huge cost and labor savings and justification for the higher initial cost of the LR, skimmer and refugium. Marine systems have far out-striped filter-based tanks in savings on water preparation and usage.
10.
“Here is a quote on marine systems,..”
I will not repeat that quote, but the chemistry stated is not basically incorrect, just a bit wrong-headed. IMHO, a SW tank, especially one with inverts of any sort if just LR & macroalgae and amphipods, is not a marine system if the pH is 7 or below. It is chaos and a failure – which may or may not be immediately obvious, NIMFT, not now, not in the past, and not in the future. That is not a marine system. It is a disaster.
11.
“There really is more we (as hobbyists) need to test for under these "unique" circumstances. Although aragonite stagnation is not new to SW enthusiasts, it is something that should be considered for new F8 owners. Possibly add this to the Pufferpedia care sheet along with recommended testing for Alk and how to adjust those levels?”
There are lots of things that can be tested and monitored. There are even many things that should be tested for routinely in particular types of tanks. There are also multiple ways of adjusting any given water parameter. For F-8s, I chose RF w/aragonite for myself as being simple and trouble-free once established, but it does require additional aragonite over time. I would not use that technique in a reef. One solution does not necessarily suit all systems, in fact is unlikely to do so.
That is more than enough to answer your first post. In a day or two I will add more, but my computer time is limited.
HTH.
!
