20 Gallon Tank How often should I do a water change?

Hey everyone, I have a 20 gallon planted aquarium which is heavily stocked and I’m wondering when I should do water changes and how much water I should be changing. I did an experiment and found that my tank produces 20ppm nitrate per week. I’m trying to avoid having over 40ppm nitrate in the tank at any time. Should I do a water change once or twice a week? And how big of a water change? I’m also wondering how much nitrate I should have in my tank for optimal plant health/growth. Thanks!

 

Hey everyone, I have a 20 gallon planted aquarium which is heavily stocked and I’m wondering when I should do water changes and how much water I should be changing. I did an experiment and found that my tank produces 20ppm nitrate per week. I’m trying to avoid having over 40ppm nitrate in the tank at any time. Should I do a water change once or twice a week? And how big of a water change? I’m also wondering how much nitrate I should have in my tank for optimal plant health/growth. Thanks!

Oh god, has this been debated. Even here on fishlore, you'll get lots of conflicting opinions. I personally believe in 50% water changes weekly, high nitrates or not, just to replenish minerals and such. The keyword is believe, I'm way too busy and lazy to do that. Realistically I do a 20-40% WC every 2 weeks, which may be part of the reason my substrate has string algae. If you have plants and you're only going for low nitrates, then you can do water changes even less frequently. Aquarium Co-op made a great free infographic detailing how to carry out water changes to keep nitrates low, so you can check that out.

In terms of your goal, if you're producing 20 nitrates per ppm per week, just wait until levels rise to 40%. Then do a weekly 50% WC and you'll have 20-30 ppm usually in your tank, which isn't bad at all. Or you could just add more plants, either work, I'd prefer both.

 

Hey there!

It's pretty common practice to do a 25% water change per week. This is especially handy for a 20 gallon tank, as it's one big ol' bucket each time. Amount and frequency are two main factors at play; if you're the sort of person who likes to REALLY do a job less often, you could do 50% every couple weeks, or if you are super excited about tank maintenance (this is especially easy if you only have one tank!) you could do 15% a couple times a week.

40 PPM is a reasonable boundary; nobody's likely to get hurt at those levels, but it'll feed the plants you've got. You can A) test a bunch of options until you find the parameters you like, OR B) try a few styles of maintenance routines and see what you like, then check to see if you're comfortable with the parameters it gives you.

Remember that either way, things in this hobby grow. Your cute little trio of guppies could become a hundred guppies in a year, and that little hitchhiking piece of frogbit will eventually grow to cover your water surface, and each side will impact your nitrogen levels in one direction or another without some degree of intervention on your part.

 

50% weekly should keep it at around 20ppm which is safe for fish and enough for plants. If it’s a low tech tank you could do larger changes. I find that my plants in my low light tank do fine with nitrates usually around 10ppm.

 

I also like 50% water changes and have always done them. To me the more fresh water the better as long as you’re matching PH and temperature. More than just nitrates accumulate in the tank and you mentioned its heavily stocked also, so I’d aim for more then less.

 

The bigger water changes you do weekly keeps your tank closer to your source water so it does not shock your fish as much when you do a water change. I do 50% weekly.

 

The truth is ( in my opinion) we all feed different foods in different amounts to different species.
We all have different amounts of ornaments wood and rocks taking up water space. We even all fill the tank to a different level.
My suggestion is to put a mark on the side of the tank at 45%- 50% of the heigh. Then allow for solid objects ornaments etc. Having picked a mark stick with that amount exactly for 4 or 5 weeks. At the end of 5 weeks you will know if the nitrates are increasing or not. Once you have established that once a week OR TWICE to that mark is your minimum feel free to do extra water changes mid week or any time you like .

I change what looks like 40% - 45% each week but I know with all the ornaments/ objects in tank it is at least 50% . I often change a little water in the middle of the week as well as I clean a filter etc.

As StarGirl wrote the more often you change water the closer the tank water is to the change water. .