> Off the Cuff: Fish Tank Changes! – Plant Daddy YQG
Off the Cuff: Fish Tank Changes!

Fish Tanks -

Off the Cuff: Fish Tank Changes!

Off the Cuff is a series of blog posts that started off as Facebook comments! Expect imperfect phrasing, the occasional typo, and a wide variety of topics! Make sure to follow us on Facebook to keep up with our comments -- and ask us any questions you may have!

As many of you might know, I love fish tanks almost as much as I do houseplants -- and I got into them because of houseplants! To me, the two hobbies are linked -- I use my fish tanks to raise humidity in my plant rooms and to propagate new cuttings (and to just grow a couple houseplants per tank!), and I use the fish tank water nearly exclusively as the water for my houseplants -- it comes pre-fertilized with all the micronutrients that they could need (though I still add NPK chemical fertilizer)! 

So "how often should you change your water" is a bit of a moot point for me -- I'll change a tank every time I need more houseplant water, and that's a consistent enough schedule that my fish stay happy! If you aren't like me and in that happy balance, though... How often should you change your water? 

Well... "How often should I be doing a water change" is unfortunately a question with a million factors that goes into it, so it's hard to say. Here are a few of them, though!

• When you do a water change, what % of the tank are you changing? Small changes need to happen more frequently to keep nitrates at bay.

• Are there live plants in the tank/how densely planted is it? Heavily planted tanks don't need water changes as often, since the plants uptake some of the nitrates, and tanks with no live plants at all will need more frequent changes.

• Are you using substrate, and if so what kind? Substrate doesn't harbour as much beneficial bacteria as filters, but it DOES hold a significant amount of it. A tank without substrate will need more water changes, and one with a substrate that has more surface area (think bioactive substrate vs aquarium gravel!) will need fewer.

How stocked is it for its size? There are a few online calculators you can use for this, to get an idea of how stocked it is. Obviously, more heavily-stocked tanks need more frequent water changes.

How is the filtration for its size? The more filtration that a tank has, the more area there is for beneficial bacteria to colonize, and the less frequently you'll need to perform water changes.

How do you feed? Does there tend to be leftover food amongst the substrate, or none left at all? If you're overfeeding -- the fish aren't eating all the food you're putting in -- then you'll need to do more frequent water changes.

There are a bunch of other factors too (how quickly water evaporates, for example), but those I think are the biggest ones, unless I'm forgetting one that's staring me in the face.

The best way to check how often your tank needs water changes is to get a test kit (ideally not the strips, they're good in a pinch but can be inaccurate sometimes), and test your water regularly after your next water change. If you show any ammonia or any nitrites, your tank isn't cycled (or your cycle has crashed, or something has happened), and you should first do a significant water change and then dose with Prime.

Nitrates are okay at certain levels (again, depending on a few factors, primarily species of tank inhabitants and whether or not you have live plants; "Okay" can range from 20ppm to 80ppm, and I've seen justifications for higher). Once you're consistently showing 0 ammonia and 0 nitrites, and your cycle is stable, do a water change and then test your tank regularly (even daily) until your nitrates are too high for your tank, and then do another water change.

That should give you a baseline for roughly how often YOU need to do a water change for YOUR tank.