TOPIC: partial water changes

Q: My betta is in a 1/4 gallon acrylic tank.  The fish wrangler at the pet store insists to NEVER change 100% of the water, always to retain 1/2 of the water with the new (I use bottled spring water), but your webpage says differently. Please advise...

above question submitted by Lucy, Los Angeles - CA

Ahhhhh, pet store helpers.... They would help everybody a lot more if they refrained from helping (or trying to) LOL.

Here are a few facts to help all of you with bettas in SMALL bowls/jars/containers. But first let's define "small"> I would qualify of "small" any bowl that is 1 gal and under.

So if your betta is currently in a 1 gallon (or less) jar, or if you prefer in simple mathematical equation:

if betta jar =< 1 gal   then owner = 100% water change weekly

get it? ;)

Well, having said that, the pet store guy wasn't entirely wrong when he talked about doing a partial water change (partial water change = changing only part of the water as in 20% to 80%). In most cases, when you own a fish tank, you never want to change all the water. Say you had some gouramis in a 20 gal tank, with a power filter or undergravel filter. I would then recommend to do only a 40% water change every 6 weeks (depending on how many fish are in the tank, how big a filter etc... - but this is just an example to illustrate my point) and I would tell you to never ever do a 100% water change.  This theory is correct and is to be applied to just about all fish set-ups .... EXCEPT FOR BETTAS that is. Bettas ARE the exception to the rule. Hence Mr. betta expert at the pet store needs to brush up on his betta skills ;).

Here are a few points about full water changes:

  • when a jar is so small (1 gal and under) it cannot have a filter and so the water is just sitting there, waiting to get as dirty as it can as fast as it can. And it can :). Get dirty. Fast. The level of ammonia and nitrites rise at an alarming speed and rate, and poison the fish. In most cases a small 1/4 jar like yours (hey girl, you need to make another trip to the store and get a 1 gal jar for your fish asap!!) will get unhealthy for your fish within 3 days of changing 100% of the water 9yop, you heard me right, I did say 100% LOL). It may still "look" ok to you (not green, not a bunch of stuff floating about in it) but in reality WHAT YOU CAN'T SEE CAN AND WILL HURT YOUR FISH! As an experiment if you were to clean your betta's home and put brand new water and test it for nitrite your first test result on day 1 would be a nice light blue color (GOOD). On day 2, it would be a pink color (NOT SO GOOD). On day 3 it would already turn to purple (BAD). So as you see the test kit would clearly show that you need to replace water on day 4. Also the more you feed, the faster the process of pollution. 

  • now that it has been established that the water in a small jar becomes unhealthy within a few days, let us look at what we can do to fix that. A water change :)) ! (yeah, I know, to some of you rather lazy betta owners, this is a NEW concept LOL) (now let's all repeat after me: WA-TER CHAN-GE).. Good. Now if you were to take that 1/4 gal jar after 4 days (purple color) and change only 50% of the water, and if you were to test it again you would get a light purple reading (NOT SO GOOD) on day 1, a purple on day 2 (BAD) and a super extra purple on day 3 (AGHHHH). That is because a 50% water change in the context of a very small body of water (with one hungry piglet betta in it LOL) is not sufficient to bring back the balance of nitrites to normal or acceptable levels. If you had a filter and say 2 gal of water, it might do the trick just fine, whatever slight nitrite might be left would be absorbed by the carbon of your filter. But in a 1/4 jar, no such luck :((.

So in short YOU GOTTA DO 100% WATER CHANGE ONCE EVERY 4 DAYS. PERIOD. (for 1/2 gal jar once every 5 to 6 days acceptable - and for 1 gal jars once every 7 days OK). Also the larger your betta, the more you feed it and the more often you have to do the water change. (Please do not starve your betta cause you are too darn lazy to do a water change every 7 days! GRRRRR)

Now on how to a 100% water change safely:

  • prepare water ahead of time, treat it and let it sit for a day or two. (In you case Lucy, no need to treat it cause you use spring water).

  • when comes time to change the water of your fish make sure your new water has the EXACT same temp as you betta's water. A good trick to achieve this: Buy another jar of same size and fill it with the new water and place it right next to your betta's jar 24 hrs before doing your water change. 24 hrs later, you can use that water: it is now at perfect temp.

  • always use the same water (treated with the same chemicals in the same way). Any changes would be hurtful and possibly even fatal to your fish. Can't switch from bottled water to tap water to distilled water etc... This is a BIG NO NO.

  • for all details on how to perform safe betta friendly water changes, see my water page. :). 

PS: better give your fish store contact my website address ;), seems he could use it :)) LOL. (No hard feelings :)) I just like to tease).