Water changes. Do you use any indicator of when to do them?

[brewmaster15]

My guess is that given the frequency of changes recommended, all would have nitrates under 10 except possibly anewbie. Also the issue of drip systems raises the discussion of average levels (i.e. area under the concentration curve) vs max levels. What I mean is that a 100% wc done once daily will have a contaminant value e.g. nitrate that varies from 0 to X. A system that changes 100% water over the same 24 hours with a constant flow drip system will have a nitrate level of X constantly. With his system I would first try to do large changes every 2-3 days and follow nitrates and see if dropping that level changes the behavior of his discus. If so then I would increase the drip volume.

What I do not get is that one of the things beyond nitrates and DOCs is bacterial levels and most pathogenic bacteria have doubling times measured in hours, not days. I am committed to using UV and from an infectious disease standpoint do not see the downside other than the cost of replacement bulbs.

There isnt really a down side to them except the added cost and in recirculating systems they can definitely be a benefit. The only other downside is they only kill organisms in the water column. They can be a good addition to a tank.


Don you aren't wrong either on the rates bacteria reproduce but I think we always over simplify the bacteria component in this.Guilty of it myself. We say Discus dont like high bacteria loads.. which does seem to be true and the water they evolved in definitely lacks high bacterial loads being so soft and acidic.

But in our tanks I dont think its really "bacterial loads" .. Its "pathogenic bacteria loads "These bacteria generally thrive on fish food and wastes, as well as thrive in dirty water and waters high in organic loads. Most bacteria arent pathogenic to fish and often act as inhibitors to pathogenic strains... but if we give the pathogenic ones a chance to multiply.. they can over run the tank.

Thats were water changes and hygiene come in.. These can remove the wastes and allow for a healthy balance..Even in Aquaculture systems that rely on recirculating systems and Uv they have to remove the solids and organics for a healthy system to occur

[Willie]

yeah, UV is starting to become increasingly attractive in my eyes as well, from a bacteria management perspective

So this is a misconception. UV radiation causes dimerization of DNA base pairs and prevents bacteria from replicating. However, virtually all bacteria live on tank surfaces, including the glass walls and bottom, substrates if you have them, heater tubes, etc. Inhibiting growth of all the bacteria in the water column has little to no impact on the overall level of bacteria in your discus tank.

UV treatment is primarily effective against blooms caused by blue-green algae, which is a bacteria. It'll also reduce the population of single cell protozoa (non-bacteria) in the water column.

[dspeers]

Use of UV does raise questions that are not well researched at least when googling via google scholar.
1. Does the bacterial concentration in the water column correlate to what is colonizing all the hard surfaces or are these to some degree separate bacterial populations. The assumption is that pathogenic bacteria prefer the water column or at least are only pathogenic when in the water column rather than attached to a hard surface.
2. Whether the bacterial counts do go down in general with UV is demonstrable but there are some concerns that certain pathogenic strains are more tolerant of UV and are therefore given a competitive advantage as beneficial bacteria are selectively more inhibited.
3. How well does bacterial concentration correlate with disease burden reduction and what exchange rate and UV intensity are required to maximize that effect.

Regardless, my understanding is that uv systems are extensively used in commercial settings with at least some expectation that they reduce disease burden, and if nothing else do result in more crystal clear water. When I used them when they were first introduced for home aquariums in the late 70s I was pleased with the results. To me the water was clearer and infections were markedly reduced, but who knows, maybe only an expectation bias.

[brewmaster15]

Regardless, my understanding is that uv systems are extensively used in commercial settings with at least some expectation that they reduce disease burden, and if nothing else do result in more crystal clear water. When I used them when they were first introduced for home aquariums in the late 70s I was pleased with the results. To me the water was clearer and infections were markedly reduced, but who knows, maybe only an expectation bias.

This is 100% true. UV is used commercial setting extensively and I suspect that if we search for aquaculture papers on its use, we might have a better understanding of what its uses and limitations really are.

[RevClyburn]

okay, so water changes are important, and everyone will have their own opinion on when to do them. I'm about to set up a discus tank, wanted more than just freashwater fish. I have had a saltwater reef, with inverts and angels. And took it down when I bought this hose with the pine floors. Didn't want the salt to tear them up. ANYWAY, need to know what you are doing to your water, are you adding a chemical or just straight water that's been sitting a couple of days? And some of you have a sump, would love to see how you have that set up. I have mines from the reef tank, could I use that? What media are you using in it? And do you have check valves on you pumps, power failures can be a disaster, spekaing from experience.

[brewmaster15]

okay, so water changes are important, and everyone will have their own opinion on when to do them. I'm about to set up a discus tank, wanted more than just freashwater fish. I have had a saltwater reef, with inverts and angels. And took it down when I bought this hose with the pine floors. Didn't want the salt to tear them up. ANYWAY, need to know what you are doing to your water, are you adding a chemical or just straight water that's been sitting a couple of days? And some of you have a sump, would love to see how you have that set up. I have mines from the reef tank, could I use that? What media are you using in it? And do you have check valves on you pumps, power failures can be a disaster, spekaing from experience.

Edwin it would be easier to give you guidance here if can give us information on your water,tank size, goals as far scaping the tank, etc. There is not a one size fits all way to do it but based on your particular situation we can offer relevent suggestions..
al