Water Changes - Is Even More Better?

The bio-load of a tank is defined by the number of fish and waste production by those fish. It is an unquantified value and is generally just refered to as high, low, or fine.

The relevant term is the size of the bio-filter, which should be limited by the bio-load. If bio-load is not the limiting factor, in other words, if surface area or O2 are limiting then the tank is improperly filtered, overstocked, or poorly maintained.

Aeration is mostly decorative since most folks don't produce bubbles fine enough for efficient gas transfer. The shearing force produced by the filter return is more efficient at aerating the water than the bubbles produced by most air stones. For efficient gas transfer between bubble and water, you need a Reynolds number lower than 1, which means that for most systems bubble size must be smaller than 1 mm.

That said, air stones are fine for providing a little more circulation, but given the noise produced by most air pumps - or the price of the good and quiet ones - I'd just as soon buy a powerhead.

Sorry, undefined term.

The Reynolds number is a non-dimensional term used to define whether fluid flow is laminar or turbulent. It is velocity times the diameter of the bubble divided by the viscosity of the surrounding fluid. For this definition fluid can be either the air or the water.

Gas transfer in turbulent systems is tricky to calculate and is less efficient than in laminar flow. Laminar just means that there aren't any drag currents, the water just flows smoothly around the bubble.

The number or colony size of the nitrification bacteria is determined by the bioload in the tank. The more ammonia generated in the tank, the larger the colonies - which will be located where the conditions for them are optimal*. Water change schedules or volumes exchanged should not affect this signiciantly unless you are set for constant flow-through of new water by automated water changers (quite a number of commercial breeders do this - 200% or more daily changes, distributed over the 24 hour period or continuous low flow). Happychem has already addressed the math on that.

Remember that we use nitrate concentration as an indicator of general pollution, as it is the pollutant most easily measured. All of the organics are beyond our view. The closer the water parameters are to your source water, be better the tank will be. There is no rule of thumb that can easily be applied, as every tank is different.

Planted tanks don't give us an indicator, as they use up nitrate depending on the lighting and supplements (many planted tanks need nitrate added), so we simply adopt the same change schedule we use for our FO tanks - say 50% - and this also relieves us of much testing (expensive, time-consunming) as changes at that scale reset the levels of added nutrients which have not been used such that we will never be more than 2x the added nutrient concentration.

It is not possible to change too much water**, but somewhere on that scale you hit diminishing returns - where that level is for your tanks, only you can judge. Even at that level, it is not a bad thing to periodically do your regular weekly partials much more frequently(quarterly, semi-annually, at least annually) - say every day or every other day for three changes or so - to do a 'deeper' reset than our routine 50%.

*That is, where the water flow is highest (for delivery of nutrients and oxygen) and where they are protected from suffocation (i.e., the water flow has been mechanically prefitered such that the bacteria are not not buried in mulm), and where there is sufficient substrate for their attachment (they cannot metabolize other than when attached). Normally the large majority of these bacteria will be in well-maintained filters. If the filters are less than well set up or maintained, then they will anywhere in the tank which does favor their requirements.

**With all the standard assumptions - disinfectants have been neutralized, the water parameters of the input water are similar to the tank water, etc.

I stand corrected and learned something new. :bowing: :bowing: :bowing:

My thought was you are turning over the water 50% every three days, eventually, there will be a time when you are basically re-cycling the tank. Apparently this logic is incorrect and disregard any previous statements.

Aries

That's one of the classiest things I've ever seen on a forum

Roan Art,
I can believe the difference that 2 or 3 50% water changes a week make in the color and vitality of your bettas. I use a phrase a lot; "freshwater fish love freshwater". You are seeing why that is true.

Routine water changes do a lot for your fish. And your ability to manage a tank. To me one of the most important consequences is the establishment of a water chemistry stability that will not be fundamentally altered in the time of an emergency (ie., fish health issues requiring some form of medication). Many times hobbyists put off water changes--or change small percentages every couple of weeks. The DOC's, nitrates and other metabolic by product cannot be exported in quantities matching their generation. With an infrequent, or low % of water change you are slowly but surely establishing the requisite conditions for "old tank syndrome".

So, let's talk about nitrates and their relationship to other factors in the tank relating to fish health.

Nitrates in and of themselves have been poorly researched--as have most topics fish related. Especially as directly related to the "hobby". Better work has been done in the aqua culture (or food) aspect of fish keeping. Often times the best place to go for research data is at the University and Commercial levels.

The relationship of increasing nitrates and increasing DOC's has been documented. The relationship of DOC's to parasitic and bacterial nutrition has been documented as well.

Discus, and many other SA's come from extremely low (non-existent) nitrate environments. They have a natural sensitivity to the presence of nitrate in the water. This sensitivity has been anecdotally related to otherwise unexplained death (at levels as low as 20+ppm's). Will fish acclimate to nitrates? Yes. There comes a point, however, where you trap yourself. A hobbyist finds himself (or herself) unable to perform any type of substantive water changes that may be required to address the presence of fish disease and/or fish death. They have problems even addressing general fish health and activity levels. Water chemistry issues pop up, that in turn creates more fish disease and death.

Acute toxicity as a consequence of nitrates is perhaps part of the question. Acute nitrate toxicity/death has been reported, depending upon species, in ranges from 187ppm up to 6000ppm. This was not acute toxicity upon introduction to high nitrate levels--rather acute toxicity achieved at the end point of acclimation.

Acute toxicity (nitrate shock) has been reported in many species at levels as low as 40-60ppm with sudden introduction.

The effect of nitrate on reproduction has also been reported in red leg frogs, African clawed frogs, benthic crustaceans, and several species of North American fish. Reproduction impact with frogs and benthic life forms was pronounced. The rate of reproduction in fish parallel the other life forms--but not as pronounced. Decreased spawning frequency, reduced fry count, and smaller offspring (3-6% decrease) was reported.

Digestive disturbances, as well as reduced oxygenation of blood have also been reported as nitrate levels increase.

The generally accepted level of immediate nitrate (if fish are allowed to acclimate) damage seems to be 80-90+ ppm's. At the same time the researchers all seem to point to a gradual, negative health impact at lower levels.

As pointed out the dissolved organic compounds (DOC's--hormones, pheremones, lipids, amino acids and other fish by product) are one of the key reasons for nitrate levels measurement in the hobbyist’s tank. Both seem to accumulate at relatively the same rate.

Our fish originally come from an environment that precludes the natural presence of nitrates. Breeding at farms and in tanks has certainly changed the equation. The size of specimens in the hobbyist tank is certainly evidence of that. Even fish that have been provided ample space, good diets, clean water--basically an environment conducive to good health--never achieve the sizes attained by their 'wild' cousins. Research seems to indicate that the nitrate levels you report would result in the 'small fish' phenomenon. And, too, the presence of hormones emitted by certain fish that work against the growth in other specimens.

At the same time, it has been well documented that certain breeders achieve "cleaner" environments than others. The breeders that maintain less stringent conditions have often times shipped fish that are full of parasitic and bacterial problems. Maybe the fecundity of the fish is reliant upon resolution of unseen health issues by the hobbyist at the time of purchase. Without that immediate resolution the asymptomatic issues fester, doing internal damage, then when symptoms appear it is too late for many hobbyists to "save" the fish. The level of stress achieved when symptoms present often times mitigates the ability of the immune system to respond to the issue.

It seems to me that many of the well recognized breeders do not really keep "sterile" environments. Rather, they achieve a water chemistry that closely parallels that of the "natural" environment. Resulting in fish more acclimated to their natural environment. Creating sensitivity issues when introduced to local conditions.

Flexibacter is fairly typical cause of disease. This is a bacterium that flourishes in water above 7.0 ph. A ph level that is not found in the waters discus have evolved in. In the wild discus receive very limited exposure to this bacteria. Discus bred in conditions mirroring the wild share this issue. It may not be a case of lost immune capacities. It may be a case of nurturing fish when introduced into an environment that is alien to them. The ph of many of the breeder’s tanks (and the wild) almost assures that the fish are not exposed to pathogens that will be present in the hobbyist’s tanks. Maybe the attention (or lack of) paid to water changes and tank maintenance that permit pathogens to multiply far beyond the levels historically present in the natural environment is not indicative of lost immune response--rather it may be a case of an immune system that is incapable of mounting a defense against overwhelming odds.

There are many stories of "amazing success" achieved that fly in the face of conventional fishkeeping wisdom. There are many more testimonials that indicate the "success" may have been more than a bit of luck. The gonadotropic response required for breeding of fish species is many times a delicate balance of water chemistry, environment and temperatures. Breeding activity in high nitrates is not unusual—fry survival is though.

It gets back to "freshwater fish love freshwater". Provide that and you will be providing a clean and stable environment that fosters fish health, growth and fecundity.

I have often said to newer hobbyists tthat "we are keepers of water, the fish just come along for the ride". It is a slightly different perspective on the hobby. It requires an examination of what we do from a different perspective. If you buy into it then you realize that "what's convenient" is what permits our fish to survive. the extra 20-30 minutes a week is what permits our fish to thrive.

Sorry, it was sort of rambling. But, I get like that--lol

There is an old saying that is sooooo true "you take care of the water and the fish will take care of themselves"...