Understanding Water Changes

Discussion in 'Water Changes' started by BrettMad, Jul 31, 2017.

  1. BrettMadNew MemberMember

    Something I like to try to get a handle on. In reading I can see that there is a wide range of opinions on water changes. How much should be changed, how frequent and what are the factors that help make those decisions.

    In one of my other thread someone made the point that every tank and every person is different, and what works perfectly well for one tank might not work as well for another depending on inhabitants, environment and other factors.

    So I guess what I like to ask here is, what is accomplished by the water change? Hopefully that will help me see the reasons for some of the differences of opinions.

    One thing I know that the water change will do is reduce the number of nitrates in the water. If you are replacing water that has been in the tank for some time with water that is fresh, whether it is Ro/DI water or tap water. This dilutes the nitrate level. Nitrites and ammonia should be unaffected because in a well-timed cycle tank those are being removed by the bacteria as fast as they are being created. This would suggest that the frequency and amount of water being changed would be what is necessary to keep the nitrates at an acceptable level since they will not be eliminated. In this case, planted tanks would need (theoretically) less water changed and/or less frequently because the plants would absorb some of the nitrates, slowing the rate at which it builds in the tank depending. This would also mean that bio load would matter, with many fewer fish the same tank would need to be changed less often. If this is the primary governor of water changes, how much is too much nitrate?

    Another thing you can obviously do is clean the substrate/sand/whatever you have at the bottom of the tank. My first water change with that was somewhat humorous, I either was not getting any of the substrates circulating in the larger part of the vacuum to or I was filling the whole thing up! I can tell that is can take more practice. The question again becomes what are we cleaning, are we removing wastes so that they will not go through the nitrogen cycle, thus reducing the amount of nitrate that we eventually have? Are we getting rid of other debris? If this is the primary driver of water change, it seems like the amount of water would matter less than whether or not you are able to clean most of the substrate. In this case the frequency should be related to how dirty the tank gets, which is probably also related to the bio load and perhaps the specific inhabitants.

    I know there are factors, such as getting ich, that would cause a change in the normal rates.

    Anyways, I was hoping that some of the veterans or more experience beginners would talk about what they see as the purpose of the water changes that they do. I assume that you will talk a little bit about your frequency and amount of water you change in explaining the reasoning and what you are trying to accomplish, but I am primarily looking at the reasons and not just the amounts and frequency. As I already stated, I know there is a fairly wide range of opinion there.

  2. AllieStenFishlore VIPMember

    Hi there. One reason to change the water aside from cleaning and removing nitrates is, that you are replenishing the minerals in your tank. Tap water has minerals necessary for a healthy tank. You can add chemicals to the tank to accomplish the same thing, but why? When a water change works.

  3. NightShadeWell Known MemberMember

    Totally agree with @AllieSten! And would like to add that when using RO or Distilled water, you need to add in minerals to begin with (the "chemicals" AllieSten referred to), because the very definition of RO DI water is that it has all the minerals/salts removed (assuming you've kept up with your RO's filter & membrane changes lol)

    Also, I agree with why add in chemicals to do what a water change does! For one exception, I'm realizing that with how soft my tap water is {TAP ~ Liquid Test: PH - 6.2 Strip Test: KH - 0 (can't remember GH, but it is "Soft" according to Strip Test) but I'm waiting on GH/KH liquid test kit to arrive} I may NEED to add in some type of remineralizer like people do when using RO (I keep Mystery Snails & absolutely have to add in calcium, but I am sure Calcium alone is not enough...) but that's for another discussion lol! I just thought I would throw this info out there, because it is an important factor that has a lot to do with water changes - i.e. water quality... because Calcium, as well as Magnesium & other minerals... gets used up - even more so when you have live plants

    ETA: I usually do a 50-60% w/c on all my aquariums once a week - adding in Calcium, fertilizers because I have planted tanks, Prime, & a little Stability when I think of it (already have cycled tanks, just add for peace of mind b/c I have low ph - which I buffer up to around 7 {depending on which aquarium} with crushed coral/aragonite sand in my filters)

    Last edited: Jul 31, 2017
  4. Cranks_TanksValued MemberMember

    The biggest reason for water changes is to remove nitrate. How much and how often to change isnt rocket science and no general rule of thumb is necessarily correct. You can have 1 guppy in a 200 gallon tank and only need to do 10% a year, or you can have 10 oscars in that tank and need to do possibly 50% multiple times a day.
    Both stocking and your feeding habits affect how much waste is produced in a tank which translates to a faster buildup of nitrate. I like to keep my nitrate under 20ppm which works out to about 30% water changes a week, and I'll do a 75% once a month as an added safety. You'll have to test your water before and after water changes and figure out how much you have to change and how often. Generally, I say heavily stocked tanks should have water changes weekly, medium loads every other week, and really light bioloads can be once a month or longer, especially if heavily planted.

    You really dont want to go too crazy if you have plants, though. Having almost nothing in the water will allow algae to grow, having a little bit lets the plants take up the nutrients first. It's a fine balance and it gets easier as your tank gets older, the balance is easier to find. For example, my 30 gallon low tech planted tank that i light with 2 t5s and its in front of a window has almost no algae. what algae i do have is controlled by my bristlenose pleco and a couple mystery snails.
  5. Philippians 4:13Well Known MemberMember

    Why do we want to remove nitrates? I thought they were good!!
  6. Racing1113Well Known MemberMember

    Nitrates are still toxic to fish in high numbers.
  7. JesseMoreira06Well Known MemberMember

    you should always want nitrates to be under 20ppm, at high numbers they start to become toxic to fish.
  8. Cricket lynn mcleanWell Known MemberMember

    Do you have any issues with blue green algae? (The bacteria)
  9. Cranks_TanksValued MemberMember

    I do not and luckily never have. Finding a good balance of parameters is the best way to avoid problems in the first place. The tricky part is that every tank is completely different in its needs, but luckily all problems will solve themselves in time, especially with a little intervention from you or critters you stock.
  10. California L33Well Known MemberMember

    Good is a relative thing. Nitrites in your tank will start to stress your fish at 1ppm, and kill them at 5ppm. If you have bacterial helpers converting them into Nitrates for you -pretty much the same thing with one extra oxygen atom tacked on- then they're fairly harmless until they reach 20ppm. The Nitrates are also good for your plants, because they're a fertilizer, but you don't want them in such abundance that they harm the fish.
  11. NavigatorBlackFishlore VIPMember

    There are testable reasons why water changes work. They seem to me to operate on two levels, with the cheap testing tools we have and the laboratory ones we can't afford. Then there are the non testable ones - anecdotes and observations, that are also valuable. Here we go...

    Potentially testable
    Nitrate reduction, testable with our little kits.
    Maintenance of a stable pH in poorly buffered water.
    Avoidance of mineral buildup through evaporation.
    Replenishment of minerals and trace elements needed by plants and fish.
    Removal of growth suppression, communication and fear hormones released by fish.
    Removal of defensive chemicals released by fish (Corydoras have a mild poison, for example).
    Removal of meds, unnecessary water treatments, etc.
    Suppression of parasites like Oodinium in softer water regions, as they thrive when water gets dirty.

    negatives: If you live in a region with polluted drinking water that gives you ammonia from the tap, water changes are a whole other ballgame.
    Because API test kits are easy to use, you can develop "ammonia goggles" and start thinking the cycle is the only thing that happens in a tank, and become focused on one facet of water management, forgetting how complex what gets into H2O is.
    If you allow too much time between changes, you can create a shock situation for the life in your tank. You can drop or raise pH in minutes, or cause osmotic shock by cleaning a topped up and topped up again tank (minerals don't evaporate). If you have a tank that has climbed to 200ppm hardness, and like me, have 80ppm tap, then that would be quite a hit to the kidneys of your fish.

    Heavily planted tanks aren't immune unless you wear ammonia goggles. Yes, plants consume nitrates. But they need replenishment via minerals.

    Non testable impressions

    This is my 50th year with aquariums. I spent half that time in the no water change era, when old water was treasured, and half in the nitrogen cycle era, when water changes became the way to go. In the old water era, we were severely limited in what we could keep. A lot of easy fish now were classified as impossible to keep alive then. Our fish tended to grow smaller, have shorter lifespans (we got to buy new ones more...) and be less colourful. We succeeded. I had lovely tanks and some long lived fish. It wasn't Mordor in my tanks. But there were harsh limits.
    I always had fungus meds on hand, beside the Ich meds. Sometimes I would treat for fungus several times a year - it became routine as a problem, like velvet or Ich.
    Once I decided to try this water change approach (man, it looked like hard work)?
    I haven't used a fungus med for 20 years now. I have to go to chain stores to see fin rot, fungus, body slime parasites or hole in the head. I don't see them here. I had a ten year stretch without seeing Ich, and oodinium is now uncommon. I can breed fish we couldn't keep alive. I don't have to limit my interests to a few ultra-hardy species. Plants grow better (to me, an unplanted tank is an empty one). I change 30% every week. I never use a test kit except for hardness. I do use a tds meter. Ammonia is a minor thing to me - but mineral content is important. Water changes stabilize that.

    Totally untested here, if I look at a proper scientific test? With water changes, my fry survival rates are way higher. Miss a change even with my cycled filters, and I lose fish. Fry grow way faster - if I didn't have a job and family, I would change water daily. Adults breed more easily. They live longer. They look better (very subjective, but). Bacterial diseases are rarer, by a wide margin. I used to see a lot of dropsy pre water change - now I only see it in elderly fish at the end of their time. I see fewer parasitic diseases, although experience helps there, along with clean water.

    Swamp fish get fewer changes. My Aphyosemion killies breed poorly for 3-4 days after getting clean water. I do their changes (30%) every 12-14 days, for a pair alone in a 10 gallon. I get 7-8 days of breeding in the middle. But if I pass 2 weeks, I start to lose adults and see a visible loss of vigour.

    The ultimate test? This sounds too sensible for the aquarium hobby, but go stand in a healthy stream. Feel the water move around your legs, watch it flow. There is no filter sending it around in circles. It is being replenished. This summer, if you stand in a stream here, you'll get soaked by a big rainstorm within minutes, it seems! We put on our wee goggles and stare at API ammonia readings, when we could supplement that by remembering the big water cycle, of rain, evaporation, replenishment flow... in an indoor tank, that's our responsibility.
  12. BettaPonicWell Known MemberMember

    I personally prefer fifty percent weekly. I think it gets more nutrients for the plants. I also need to get gunk out.
  13. BrettMadNew MemberMember

    Thank you to everyone who replied. I really appreciated everyone's thoughts, and particularly thank you to NavigatorBlack for an incredibly thought-provoking post.

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