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Regular Maintenance of Aquariums

There are several elements to water chemistry that we need to keep in balance in order to ensure the aquarium is healthy.  This guide will help you make sure this occurs as passively as possible (i.e the aquarium is self sustaining) but it still isnecessary to at least monitor and in most cases do a bit of work in even the most balanced and self sustaining aquariums.


The easiest way to keep a tank healthy and most effective solution to most problems: Water Changes


Why: remove excess organic waste that creates an imbalance in the water chemistry. If not addressed, this will mean less healthy fish/coral and also give rise to pests like hair algae, cyanobacteria, and glass anemones and flatworms.  These pests are just organism seeking to bring balance to your tank because there is an excess or lack of something else.


In a healthy natural habitat, water changes are not necessary.  The waste of one organism is consumed by another so all nutrients are recycled.  This was attempted in the Biosphere in the southwest back in the 90's with hopes of replicating it on the moon or mars.  It is difficult to do accomplish in a small aquarium though. there is a strategy, called the Triton method, that uses algae in the refugium to basically pull out all nutrient and most minerals and then testing using ICP (Inductively Coupled Plasma) analysis tells you what to put back into the tank. It involves sending off a sample of water every 3 months or so to a lab where a machine tells you specifically which minerals and how much to reintroduce into your's a lot of work for not having to do water changes...


 The ideal frequently of water changes depends on the aquarium setup.  Those aquariums that can better process waste need to be changed less frequently. You can follow these guidelines as a general rule for success, but remember every tank is different:

●     Fish only tanks require the most frequent changes, generally every  2 weeks 25% tanks up to 55 gallons, 10% tanks up to 225 gallons.

●     Tanks with a good number of hermit crabs or snails: every 3 weeks up to 25 % for tanks under 55 gallons, and 10% for tanks up to 225 gallons.  Snails and hermit crabs function as recyclers, helping to break down fish waste

●     Tanks with fish + corals and plants: every month 5% and supplementing based on water tests.  Reef and plants also consume fish waste. Because of the sensitivity of marine inverts and some coral, more small changes are better, 2 x 2.5% per month with any supplements dripped in over 24 hours.

●     Reef only aquariums require water changes to replenish trace minerals which we do not generally measure. They should be tested for calcium, magnesium, and KH regularly and supplemented based on that but a mandatory 20% change monthly should be instituted to make sure that trace elements are available.

●     Keep in mind that overfeeding your fish or overcrowding the tank both require more frequent changes


Here are common examples of when it's highly likely that water changes are in order.


If you notice a quick change in your system:


Remove Dead Organisms immediately.  Leaving dead fish, invertebrates, or coral can lead to a rapid decline in water quality.  If possible, move questionable corals, plants, and even rocks to a separate system. This could even be a 30 gallon bin which you fill with water from the aquarium from which you are pulling water out of for water changes. This will remove the source of potential contributors to the water fouling. If you think that a coral is dying, it almost certainly is. You can pull it out and smell it. If it is putrid, get rid of it.


Check the thermometer.  This is so obvious that it can be easy to overlook.  A problem with the heater can be catastrophic.  The correct temperature should be 74-82 degrees Fahrenheit. Ideal is 76-78 degrees Fahrenheit.


Check the filter.  It can be clogged or not running at all (from losing prime , breaking the impeller, or burning out the pump). Make sure that your sponges and other filter media are not saturated with gunk, if so rinse them out with salt water if possible.


Check the pH.  You want the pH to be around a 8.1-8.4 . Follow this link to pH description

●     It is much more common for the pH in a neglected or acutely crashing tank to be low

●     This can usually be fixed by solving the underlying problem and then doing multiple 25% water changes. It is important to replace the water at 10% volume of tank per hour or less. For example, if you have a 55 gallon aquarium, take out 15 gallons initially and replace 5 gallons per hour.

●     If your pH is too high, it is likely that the water you are using for water changes is very hard (usually well water) or you over dosed a buffering product.

●     Using buffering products in anything but a very successful reef that is drawing carbonate for growth is a temporary fix and usually a band-aid to an underlying problem. It's like using an air freshener to cover up the smell the  dog feces sitting in the middle of your living room.


Test nitrate and phosphate levels. These are the two indicators of how much waste is being produced and not reincorporated into your system. When they are both low (nitrate under 10 ppm, phosphate under .5 ppm) and there are no other abnormalities, generally a water change is not necessary.


Observe all fish closely signs of disease : If one fish is obviously sick, look very closely at all of your fish. Even behavior changes such as not eating or not coming out as often can be signs of problems.


Water changes of up to 50% can be instituted every other day with only 10% of water being returned to the tank hourly as to not shock a system. This is more accommodated by fish than corals and invertebrates however should be manageable if done to relieve water quality issues in a crashing tank. Remember if there is any smelly rocks or questionably dying corals remove them to a separate tank/bin for monitoring. If the sand is very dirty and when moved clouds of brown are released, gravel vacuum as you do the water change.


Your aquarium likely does not need an emergency change if:

•         nitrate levels are under 10 ppm and/or phosphate levels are under .5 ppm) and

•         your KH is above 9

•         there is no toxic material in your water (degrading antibiotics, bug spray, etc.)


How to change the water:

First we remove the water using a gravel vacuum  or regular siphon tube or even airline tubing as a tiny siphon to selectively pull out old food, chunks of organics, and the bacterial mats themselves. 


Next we replace that with clean water.  It is best to use deionized/reverse osmosis water.  If your tap water quality is high, you can also use 24 hr conditioned tap water (using as directed a water conditioner to remove chlorine/chloramine used by your towns water treatment facility).  If tap water is used, test it for nitrates and phosphates to make sure you are not reintroducing more nutrient (algae growth). 



Understanding Water Chemistry

To keep a tank healthy, there are many aspects to its chemistry that need to be kept in balance.  Natural aquariums (lakes, oceans) generally do a good job of this but not always.  For example, the increasing levels of carbon dioxide in the atmosphere (now over 400 ppm!) not only cause climate change and rising sea temperatures, they also cause the seas to become more acidic.  Carbon dioxide in the air can also dissolve in the water, turning into carbonic acid. This phenomena is called ocean acidification.  


Above we gave you some basic steps to keep the chemistry in balance but it also helps to understand what makes them get out of balance.  This can help you address the underlying cause rather than merely treat the symptoms. 


Nitrogen cycle

Ensure there are proper environment for bacteria to grow and this should take care of itself, assuming you do not overfeed or overcrowd the system. Large water changes can also disrupt the balance of a system and may disturb the bacteria and create a mini-cycle. See the Setting up a tank section to understand this process and better be able to identify that something might be off.


Calcium, Magnesium, KH, and pH

Calcium and magnesium become depleted as some animals ( coral, some hard algae species,mollusks, crustaceans, and even sponges) assimilate these minerals. To deposite these minerals, organisms use the bicarbonate ion, which is the same molecule which acts as a buffer to stabilise pH in tanks. So the pH generally tends to go down as the buffering capacity of water (the carbonate ion) is used up by the corals and other organisms assimilating carbonate( calcium and carbonate make calcium carbonate skeletons). Remember that carbonate is also used up by always present nitrogen cycle and the buildup of some organic acids which no animals or plants can process.


 Carbonate amount is alkalinity (also called carbonate hardness or KH) and an alkalinity test kit/KH test kit is cheap and useful for watching the carbonate hardness of your tank. It is most commonly measured in degrees of carbonate hardness (dKH) and you want to stay between 9 and 12 dKH for reef tanks. If you don't do water changes and don't monitor /supplement this parameter, your corals will slow down growth and the tips and edges won't be as colorful ( tips colors are the actual color of of the coral before the symbiotic algae can migrate in and indicate rapid growth).


The  API test kit for KH and Calcium and Seachem test kit for Magnesium are fine for most hobbyist aquariums. The Magnesium test is a bit more expensive and complicated but worth it as magnesium and alkalinity levels need to be within range for the deposition of new skeleton by corals. Certain corals, including soft corals like leather corals and Xenia, can do well or even thrive in low alkalinity and calcium. A few durable stony corals, some species of Montipora (digitata, capricornis, spongodes), Pocillopora sp., and Pavona sp. can live in this but do not grow well. It is possible for a tank to drop down to dKH 7-8 (1.8-2.2meq/L) and/or have calcium as low as 300mg/L with stony corals living for months with little growth but no mortality. To be sure to avoid this in fast growing reefs, getting in the habit of supplementing then retesting is a more efficient method to keep up with these essential parameters for coral growth. As an alternative to testing, doing salt mixed with reverse osmosis water changes of 10% a week and watching specifically KH as an index for the other stuff if you want to do the minimal for a stress free reef. For new tanks calcium and magnesium are not as important to watch as KH as corals and purple coralline algae usually aren't draining these minerals  too hard initially. Later when everything is more established and corals are growing fast you can start developing dosing plans with supplements.

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