Water Change Frequency

[aaronnorth]

also because our tap water is loaded with CO2 so these fluctautions are more likley to cause algae if you do a weekly waterchange.

I wouldn't have thought so...after powering through the tap and splashing around loads, I would have thought the CO2 would have mainly gassed off, no?


My main heavily stocked low-tech planted tank gets water changes every 2-4 weeks, usually around 20%.
That's only because by that time the small bits of floss in the baskets are usually very dirty, and the filters intake get's clogged with bits of vallis.

I've had low-tech planted tanks go without water changes for 3 months before wit no problems at all (and that was at a time when I bothered to frequently test the water).

My high-tech planted tank gets 50% weekly.

My other small open top tanks really just get filters cleaned and topped up with RO/tap water depending long how long I left it.

the CO2 is really "well disolved" unlike our fish tanks which takes a lot longer and harder to complete. Plus there is only a short period of time that the water is splashing, there wouldnt be enough time for it to all gas off. You can tell that there is CO2 in the water by testing ph of water after a few hours etc. I am sure you are aware of that test.

If you have a lot of live plants, it's possible that the nitrate never will rise much as the plants use the ammonia before it is processed thus no nitrite or eventually nitrate. Is a low level good? Probably depends on plants you have. Some people have to add nitrate to their tanks to keep their plants healthy so in their case, low nitrates aren't too good as they have to buy it and add it.

It depends on the lighting levels, higher lighting means higher demand for nutrients, but even in a "low tech" tank i wouldnt want the NO3 to drop below 10ppm, it is better to have a small amount there rather than none!

 

[Dan Robbins]

Very interesting this topic. Whats even more interesting is different people's response to the topic.
I myself have kept fish for many years and am currently in the process of publishing a book.

I do a small waterchange about 4 times a week on my tank of under 10% on my 500l tanganikan.
It keeps all my reading very stable and consistant and my fish are thriving.

However, I do not feel this a neccesity, infact, iv kept water stable in terms of Ammonia, Nitrite, Nitrate, pH, GH,KH, and PO4 for many many weeks without a waterchange.
Soluble products from fish waste are dealt with by the filter which leaves very little solid waste, which can, and will simply degrade.
Dan

 

[three-fingers]

the CO2 is really "well disolved" unlike our fish tanks which takes a lot longer and harder to complete. Plus there is only a short period of time that the water is splashing, there wouldnt be enough time for it to all gas off. You can tell that there is CO2 in the water by testing ph of water after a few hours etc. I am sure you are aware of that test.

Missed that, kinda makes sense since the waters in enclosed pipes for ages, good to know .

Though I would imagine how much CO2 is in the water varies depending on water supply, don't know for sure what's typical though - how would there be so much CO2 in the tap water in the first place though? Is there some chemical reaction that ends up with it being loaded with CO2?

 

[shelaghfishface]

Anything less then 25-30% weekly is poor husbandry. If someone can't make time AT LEAST once a week to make sure their fish arent swimming in their own waste, then they have no business keeping fish imo.

hence why you need filters huh??? ya noggin you knw nothing and slag off respectable fish keepers
i hate to have to say this but in ths game you can look at the fish and detect a problem.. maybe your not that far n yet?? but they are

50% daly oscar and shrimp ( just while he has HTH)
30% wk on 200l.
everyother day on 147l ( just cos i want to)

 

[jmkgreen]

Well I'm in a slightly different situation. I have a Reckord 70 which was installed when I lived with my folks. I no longer live there and I am scouting for a tank to install in my present house to move the fish into.

Until then the tank water is changed whenever I get back to the house. Usually this means 50% water change every 2-3 weeks (I live in a different county now). While I appreciate it's my responsibility to care for the fish I've so far had no noticeable ill effects.

For the record I'm planning on expanding to a 260L tank with twin external filters. Not sure what the water change frequency will need to be on that yet...

 

[Amunet]

125gal will have water changes weekly... just did a 20% water change on it on Monday.

My other tanks usually get a water change every week... 20-50% depending on how messy things get. I've done a water change every 2 weeks though w/ everything ok.

 

[FishBeast]

Well I set my tank up when I first met my wife and I wanted her to be involved in it so I went with the fish of her choice... goldfish, pearlscales and blackmoors... sigh... I ended up losing interest in it because the fish kept eating my plants... sigh again... and now after finding homes for most the last got dropsy... so at best once a month...hense the dropsy... Ao now I am starting fresh and as soon as my fish gets better (not likely) I will start my new setup where I will definately do a 25-30% change each week. Rain hail or shine.

I have to disagree bitteraspects.
My fish are my hobby and my job and they are all well cared for. I haven't had any fish deaths in a very long time and they are all thriving.
All my tanks are overfiltered and my bigger tanks run two externals. On the odd occasion when I have checked water stats, the readings come back perfectly fine.
Please don't assume that people don't care about their fish just because they are not doing weekly regimes.

maybe you should spend a week swimming in your toilet, and see if you dont change your mind.

Don't swim in public pools then

 

[Littlemonkey]

50% Every weekend with Gravel Vac. Have large fish and lots of poop. I even clean my pond, mind you not every week.
This weekend I will be mainly removing hair algae (from pond)

 

[nickelplates]

I tend to take the view that water changes should be driven by the need to maintain an acceptable nitrate level or the need to maintain dissolved minerals/buffering capacity, For a given setup and a given supply of tapwater one of these will normally dominate the other which can be ignored as your water changes driven by the critical factor will be sufficient to deal with it.

Because I consider myself a competent fish keeper but an incompetent gardener I have no plants in my tanks, I have also never been blessed with very soft water consequently in my tanks, as in most peoples, nitrate removal is the limiting factor. So the question of how much water to change is about the rate of build up of nitrates in the water: if you have a regular pattern of water changes you will reach an equilibrium where the amount of nitrate dissolved in the water you remove at water change is equal to the amount of new nitrate produced in the tank since the last water change. Assuming new nitrates are produced from the nitrification process in the filter at a constant rate the nitrate concentration in the water will be driven only by the intervals between and size of water changes.

I don't believe nitrate test kits are accurate or precise enough to indicate how big a water change you need over one cycle of the process so I follow a regular routine and test nitrate level periodically, if the trend is upward and heading for more than 20 (yes I do keep a chart) I amend the regime to a higher level of change, if nitrate levels are below twenty and heading downward I decrease the regime to a lower level of changes (changing the level could be a change of frequency or volume). In a stable tank it is all about long term trends and adjusting the routine over a period of months.

For example in my 130l community I was changing 30l of water every week and the nitrate level was steady for many months at 15-20. Under pressure from my wife to add some bright colours I decided to increase the stocking level by adding some more colourful mid water swimmers (male guppys), sure enough over a period of weeks the nitrate level began to creep up under the 30l per week regime so I changed it to 45l a week which I have been doing ever since and once again the nitrates bump along at 15-20.

Of course I opt to keep nitrates below 20 but this is not really scientifically driven, I just feel comfortable knowing the level is this low and I can because there is only a trace in my tap water. With most fish it would be perfectly reasonable to aim for 40 in which case you could do the same change every fortnight or change half the amount every week, nothing wrong with that as far as I can see but not my choice.

I have ignored in all this the fact that the nitrate concentration actually follows a saw tooth pattern rising slowly between water changes and dropping suddenly at each change, I would not advocate following the model I have described in such a way that very large water changes are used at long intervals as I think this could cause problems but within the limits of common sense it makes sense to me.

Of course if your limiting factor is dissolved minerals and buffering capacity you would use other parameters to monitor the process and it would be nitrate levels that look after themselves but the principle would be the same. I think the most likely fishkeepers to be in that position are those with heavily planted tanks, as I said earlier that does not include me!

 

[arobinson1984]

I do a 50% water change and a gravel vac every weekend without fail

If I have any poorly fish I also do a 40-50% change mid week

Andy

 

[aaronnorth]

the CO2 is really "well disolved" unlike our fish tanks which takes a lot longer and harder to complete. Plus there is only a short period of time that the water is splashing, there wouldnt be enough time for it to all gas off. You can tell that there is CO2 in the water by testing ph of water after a few hours etc. I am sure you are aware of that test.

Missed that, kinda makes sense since the waters in enclosed pipes for ages, good to know .

Though I would imagine how much CO2 is in the water varies depending on water supply, don't know for sure what's typical though - how would there be so much CO2 in the tap water in the first place though? Is there some chemical reaction that ends up with it being loaded with CO2?

there is more CO2 in tap water than our tank water. (whether it be 6ppm or 0.5ppm which is still unconfirmed lol). This is a good ride:

http/www.barrreport.com/articles/433-non-co2-methods.html

 

[three-fingers]

Already read that post a while ago, doesn't explain anything or give any values .

Which I think are fairly critical.

 

[aaronnorth]

why did i put "this is a good ride" lol.

i thought this was beneficial:

Doing water changes adds CO2 back to a CO2 limited tank.
Plants and algae both can and do adapt to low CO2 environments and induce genes to make enzymes that concentrate CO2 around Rubisco, the CO2 fixing enzyme. Algae tend to be better at it and have a faster response time and much shorter life cycle. When we add the CO2 at higher levels, this causes the plants and algae to destroy the low CO2 enzymes and start growing without of them since they no longer need them to fix CO2 form the KH ( the -HCO3).

As it explains why algae grows when doing frequent water changes.
As for values/ levels of CO2 in the water, i dont know how much, but it does get there by accident as they dont add it because it will erode the pipes, but i can tell you they are higher than tank water,

 

[three-fingers]

Tbh I thought "ride" was meant to say "read" and that the link would be in answer to my questions I asked - since you quoted them.
My mistake, sorry .

I'm not doubting Tom Barr's knowledge, but all I have to go by is what I've read and I've not read any explanations or citations so what is said there doesn't make sense to me yet, and it doesn't help when other people cant explain it either.

So I'm reluctant to take it at face value.

I don't find that algae does grow when doing frequent water changes...however even if I did, a made up explanation like "tap water contains a high concentration of molecule X compared to tank water and this causes algae to flourish" would have just as much credibility if someone as knowledgeable as Tom Barr had said it, and would still be a useless statement.

The only factor I can think of that would explain tap water having more CO2 is the temperature difference - but even that would vary a lot too (and I'm note sure if the difference would even be big), so I'm just going to assume my tap water contains less or around about equal amounts of CO2.

Until I come across an explanation, that is.

 

[snowflake311]

Every 5-7 days I do a 40% water change some time I will take out more. I only clean my filter out when I notice it is not running well.

My poor betta in a filtered 5 gal gets 90% water changes every 2 weeks but sometimes longer. Poor little guy I know.