Water changing how much how often

[2Itiwhetu]

It was suggested on another thread that I started that it is a good job we have moved away from small water changes, and that really in the past we had no idea what we were doing.
Well, how large are your water changes and how often?
I do 25% once a week. Why? Because at 25% I can use cold water to refill my tank (garden hose in the window) there is about a 4-degree temperature drop. At 25% I can then stabilize my tanks for the pH, hardness, and other parameters (the smaller water change means that the fresh water doesn't affect things too much). It protects me if the supply water is rubbish.
I have found over the years the trend now is to do large water changes, but by doing that the problems haven't gone away. In fact, now I see people struggling to have a stable acid tank with doing big water changes. I see fish suited for acid tanks now being kept in Alkaline systems and the reference sites on the nett even saying that is fine. In the old days as fish keepers we were way more particular about the fish we kept in a tank than the aquarists now seem to be.

 

[Stanzzzz7]

It was suggested on another thread that I started that it is a good job we have moved away from small water changes, and that really in the past we had no idea what we were doing.
Well, how large are your water changes and how often?
I do 25% once a week. Why? Because at 25% I can use cold water to refill my tank (garden hose in the window) there is about a 4-degree temperature drop. At 25% I can then stabilize my tanks for the pH, hardness, and other parameters (the smaller water change means that the fresh water doesn't affect things too much). It protects me if the supply water is rubbish.
I have found over the years the trend now is to do large water changes, but by doing that the problems haven't gone away. In fact, now I see people struggling to have a stable acid tank with doing big water changes. I see fish suited for acid tanks now being kept in Alkaline systems and the reference sites on the nett even saying that is fine. In the old days as fish keepers we were way more particular about the fish we kept in a tank than the aquarists now seem to be.

I think it all depends on the individual set up and how much nitrate builds up.
Heavily planted tanks with light stocking of small fish will generally need much smaller water changes than a heavy stocked fish only system.

 

[TwoHedWlf]

I do about 50-60%/week.

 

[duanes]

Water changes usually need to be gauged on how many fish in the tank, how large they grow, and may need to be increased as fish grow and other factors including how much buffering capacity your tap water has.
There is no rule set in stone rule that fits all.
Using water parameters like pH and nitrate are good indicators of what a water change schedule should be.
If your tap water has a low buffering capacity and your pH fluctuates wildly between water changes, those changes may need to be more frequent, and larger.
If your nitrate level is 5ppm right after a water change, but in a week that nitrate concentration rises to 20ppm o more, that once per week water change may need to be doubled, or tripled, as may the volume of water changed.
The nitrate goal I set of my tanks, is a constant 5 ppm or lower, so I do a 30-40% water change every other day on my 300 gallon system.
Testing water parameters has helped me determine that schedule.

 

[MultipleTankSyndrome]

My tanks get 10% water replacements once a week, which is to be increased to 50% twice a week as soon as I can get my hands on a good Python and a sufficiently large rubber cattle trough.
I think duanes is spot on with there being no hard and fast rule. Just do what helps keep your water chemistry within the recommended range.

 

[duanes]

One other factor I neglected.
Fish life span.
If you have fish that normally only live 2 or 3 years, like some small tetras, live bearers, anabantids or other short lived fish, elevated nitrate may not be as important....
as if you keep cichlids, or other long lived species that easily last 10-15 years under good conditions, but...... under less than ideal conditions
may suffer from HITH or other chronic diseases exaggerated by elevated nitrate.

 

[MultipleTankSyndrome]

^I'll add loaches to long-lived fish, as their lifespans go hand in hand with water quality. The vast majority are completely intolerant of excessive organic waste, but will live at least as long as (if not several times longer than) dogs or cats, so they need a consistency of clean water over those several decades.

 

[Rocksor]

I don't have plants, and nitrates would be well above 20ppm if I didn't do a total of 100% water changes over the course of 7 days. I only have a huge difference in tap cold water temperature in the winter. PH is stable with the amount of water changes I do over the course of the week because my buffering capacity (KH) is pretty high 8 degrees.

 

[FahakaPapa]

I change anywhere from 60%-70% once every 6 days or so. It's a 166 gallon tank with a 60 gal sump. Only fish in there is my Fahaka puffer who is about 11.5 years old. Messy *** fish. My nitrates are usually at about 10ppm by the time I do my water change, but that brings it back under 5ppm

 

[neutrino]

Agree with Duane, what's actually needed varies. That said, barring some issue with your water source or prohibitive expense for city water, fish appreciate larger water changes ime.

As to older practices with pH and some of the other things you mention, some of those were based on assumptions that aren't necessarily (or not always) true. A common one is that SA fish all come from low pH, soft water. They don't. It's a naive concept coming from a lack of knowledge about the continent. For example, even some discus in certain wild locations see pH up to 7.8. Some fish that are listed as coming from a lower pH river are actually collected upstream in a smaller tributary with different water chemistry. Others, where the originally known location may be a low pH river, cover a geographical range of varying water conditions.

Another example of bad info from some sources are Andinoacara rivulatus and stalsbergi (the two species commonly called green terrors). I've seen people invoke the soft water SA fish notion for them, usually rivulatus because it's by far the more common fish; on the other hand I've seen people say rivulatus comes from alkaline water. Neither is correct. Both are pretty adaptable but rivulatus comes from neutral to somewhat higher pH. It's stalsbergi that comes from moderate to highly alkaline water.

There are sensitive, even blackwater obligate, species that will be more colorful or robust in softer water and some that have issues otherwise. Or some species that need softer water to breed, but otherwise aren't as fussy. However, the majority of SA cichlids are reasonably adaptable to differing hardness and pH-- within reason. All of this makes the blanket soft water SA fish thing unnecessary in many cases and misguided in others.

All of that said-- For one thing I mix warm water from the tap doing water changes, so temperature's not an issue. My tap water comes out at pH in the mid 6s and settles out in a tank about 7.4-- something like this isn't unusual, actually, so it pays to see what your tank does a day or two after a water change. Since I don't currently keep sensitive, blackwater restricted fish, this is already good for my SA cichlids. For my kapampa gibberosa I add baking soda (and a bit of Epsom Salt). Water change interval and volume varies for me, some tanks average weekly 70-90% water changes, some (lightly stocked-- for example a 135 with just a trio of kapampa) it's 10-14 days and 70-80% water changes. Nitrates are about 5% in my tanks. Feeding, tank setup, filter maintenance, and what's in your tap water are also part of the picture with nitrates.

The formula for someone else may vary, you just have to work out what works for you, but this works for me. My current generation of kapampa are ten years old, I've had them live near 20, and I've had Heros live 17 years or more, similar with some plecos species, etc. etc. I practically never see health issues. For example, in several decades keeping fish I've had exactly one very mild and quickly cured case of HITH.