Why do water changes with plants?

[Dahlia]

I was sitting here eating sushi (with roe... mmm!) and thinking about the planted tank I'll have soon, and the plants I want, and fertilizers... and suddenly realized plants must use up more of the nitrates in an aquarium than fish can produce if you have to add additional nitrates. As a non-gardening aquarist my understanding was that the main purpose of a water change is to remove nitrates, as well as the rare unpleasant chemical such as medications.

I'm not saying I am trying to get out of doing my water changes... I'm sort of weird and actually enjoy doing them because I think it's easier to stay in touch with the needs of your fish when you spend that much time cleaning their habitat. And it's sort of mindless and therapeutic... but... I'm quite the curious cat. Why will I be doing the water changes once I have plants?

 

[daveedka]

Nitrates are the easy pollutant to test for in a fo tank, so that is what we use to gauge total pollutants, and adjust maintenance accordingly. In a planted tank, we lose the Nitrate gauge (As you have surmised) but the other pollutants still build-up and most of them can't be easily tested for. So in a planted tank, water changes are even more critical due to the fact that we can't gauge buld-up, or total dissolved solids levels. It becomes more of an insurance policy to prevent things we can't see happening.
I'm new to plants as well and can tell you they are a lot of fun. Enjoy
Dave

 

[Dahlia]

Nitrates are the easy pollutant to test for in a fo tank, so that is what we use to gauge total pollutants, and adjust maintenance accordingly.

Oh, very cool to know... and it makes sense. Any idea what some of the other pollutants are, even if we don't have tests for them?

 

[djlen]

Welcome to the fun house we sometimes call the planted tank forum.

Depending on your lighting and other factors, to some extent, you will probably be dosing nutrients to support your plants.
Basically, one develops a regimen for dosing in an effort to find balance between light, fish load, bio-mass and nutrients.
For many of us, this regimen starts with a water change followed by dosing necessary nutrients, and continued dosing throughout the week if necessary.
The water change serves two purposes. It removes unwanted extra nutrients that may build up over time, and serves as a 're-setting' of the tank for the next week's cycle. I think of it as cleaning the water.
An example: Part of the regimen includes the dosing of a Trace Element mix.
Typically, these mixes contain Cu (copper) which has a tendency to build up in aquariums and can become toxic. So, many of us advocate the use of a 50% water change to remove the 'extras'.

Len

 

[TPIRman]

Water changes also replenish trace nutrients used by the plants. IMO it's hard to underestimate the benefit of frequent, large water changes for both fish and plant life. A fair question, though.

 

[RTR]

Enclosed biological systems build up significant levels of organics - hormones, phenols, proteins, all sorts of junk - none of which are subject to hobby testing. Ditto for all the inorganics - minerals, etc. that are added even to unsupplemented tanks via fishfood and water additions - being concentrated to levels beyond plant usage even in planted tanks. In planted and supplemented tanks, obviously the buildup - as Len mentioned - can go even faster, and play hob with controlling nutrient levels. Water changes are cheap, simple, and reset everything dissolved in the tank to lower levels. The older I get, or the more experience I have, the more I am convinced that water changes are the best single thing that I do to protect and enhance my fish and their environment.

 

[Timmain42]

Welcome to the fun house we sometimes call the planted tank forum.

:laugh: Ya got that right. I was thinking more like "madhouse," tho.

 

[plantbrain]

In a non CO2 tank, I do no water changes. I add water for a topping off for evaporation.

In CO2 enriched tank we can use water changes to prevent anything from building up, We dose often to prevent anything from running out in these tanks also since the growth rates are much faster than the non CO2 tanks which fish waste alone are generally enough to provide the needed nutrients.

Water changes are more reliable and simpler than testing water for all sort of parameters and faster.

Regards,
Tom Barr

 

[Dahlia]

Why would there not be a build-up in a non CO2 tank, but there would in a CO2 tank? How long has the tank you don't do water changes in been running? What's in it? That's pretty unconventional, and I'm not sure I agree with it, so I'm curious about your setup.

 

[RTR]

There is a whole school of thought, with the leading proponents being Diana Waldstad and Tom Barr, of heavily planted tanks with no supplements (mineral or CO2) and rare water changes. That particular philosophy is alien to me, but its users report good results. Not in my fish tanks, thank you very much anyway.

CO2-supplemented tanks are normally mineral-supplemented as well, so you either do a huge a battery of tests (expensive, time-consuming, and not wonderfully accurate) or you just do substantial water changes and re-dose to remove excesses and restore balanced nutrition.