Water Changes

[Archiediamond]

Before I set up my tank I read a book by the guy who edits Tropical Fish Weekly, who said that if possible I should change 50% of my tank water every day, regardless of water quality stats. All his other advice has paid off so I've been doing that but it's quite a hassle! Is it really necessary? And now that I've started, have I made a rod for my own back by getting the fish used to it? Thanks!

 

[Phantom Thief]

50% everyday sounds way excessive. Doing it improperly could easily stress the fish, or remove ammonia before biological filtration can get rid of it.

IMO, definitely unnecessary. 25% every week is a good rule of thumb, doing more or less depending upon the stocking of your tank.

Btw, i don't think this question belongs here in Emergencies

P.T.

 

[SamUK]

i do about 20% every 7-10 days and my fish are all fine.

 

[Arfie]

25% once per week is fine in most cases, in fact 25% per fortnight is OK in well filtered tanks. It depends on your filters and stocking levels ar elike, ie how much waste is produced and how well your filters can deal with that waste.

I think the 50% per day thing is used by some of the planted tank geeks along with dosing of various chemicals and fertilisers.

Arfie

 

[andywg]

50% a day would be great if you have the tank on an auto-top off feature where 50% of the tank water is drained and refilled every day. But for most tanks 10-20% once a week will be fine.

Once you are overstocking and keeping more delicate fish then the changes become more necessary. I am currently raising to around 30% twice a week on my largest tank, though my 2 DPs in a 30 gallon only get one 15-20% per week.

The main deciding factor in Water Changes will be the nitrate level. As it rises it's time to do a change. Exactly what level to change at is open to some debate. Some will say never have more than 20ppm (same as my tap water) and othres say for sensitive fish never over 40ppm.

The only research I have found on the subject is Nitrate toxicity to five species of marine fish by Pierce, RH; Weeks, JM; and Prappas, JM reported in Journal of the World Aquaculture Society. Vol. 24, no. 1, pp. 105-107. 1993 in which it is pointed out that earlier tests have shown that prolonged exposure to nitrates over 100 ppm may be detrimental to fish. This is fairly important as nitrates are considered far more damaging to marine fishes due to the operation of their osmoregulatory system. I remember a great post by Steelhealr on the subject a while ago that detailed it all nicely, but I'm damned if I can find it now...

So I take 100ppm as my upper ceiling as I have no super sensitive fish.

 

[Archiediamond]

Thanks so much for your help, everyone! I'm not too sure how great my filter is so I've bought an air pump and bubble wand and will be keeping a very close eye on nitrate levels.