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Freshwater Aquarium Basics - by Carl Strohmeyer


Start with as large an aquarium as you can afford (even for bettas).
The very BASIC principle that is to have 1-2 inches of NARROW bodied fish per FILTERED aquarium gallon is a starting point, but not very accurate. This also only applies to a standard rectangular aquarium. Goldfish are dirty and fatter, so I would triple this with them, in fact for long term goldfish health, one goldfish per 8-10 gallons is best (One goldfish per 30 liters).

Obviously longer fish need more tank width and length. I would decrease the amount of fish proportional to the gallons in a tall aquarium or hexagon aquarium.
Remember, many fish purchased can grow much larger than your original purchase size (ex: goldfish), so keep this in mind too.

What is much more important in determining how many fish you should add to your aquarium are these factors:

*The amount of surface area relative to the gallons of water the aquarium holds. I have observed many tall narrow aquariums over the years of my maintenance service where the filtration and other factors were equal to comparable sized and stocked rectangular aquariums, that general fish health and longevity were lower.
*Type of fish, such as fish that naturally produce more waste (partly
do to the type of food they eat) such as goldfish where one fish per 8+
gallons is better. Also a fish such as an Arowana that stays primarily on the surface will need a disproportionately large aquarium (I recommend 200 + gallons for just one Arowana). And as pointed out earlier, you cannot compare a heavy bodied cichlid for instance to a narrow bodied tetra of similar length.
*Filtration, a properly filtered aquarium (good bio filtration, good mechanical filtration, and good circulation) with multiple filters is important.
*Maintenance schedule that includes regular efficient water changes
*Well maintained water chemistry (including kH and Redox)
*New or experienced aquarist; a new aquarist needs to start with a much less crowded aquarium.
*After proper feeding, good cleaning routines (20% water changes with a gravel vacuum once per week or two), proper feeding routines, good filtrations; If after all these are checked off and you still have nitrates that struggle to stay below 40-50 ppm, you probably have an over stocked aquarium (especially if there are live plants!). Also a kH and pH that starts out at proper levels, but then drops quickly after water changes and/or addition of stabilizing chemicals or products such as Wonder Shells can indicate over stocking (as well as other problems such as mulm buildup).


I always recommend two filters minimum per aquarium for redundancy and for improved biological (denitrifying) filtration. For a small aquarium, a combination of a
hang on the back (power) and a sponge filter. Or a sponge filter and an internal power filter. You want to make sure and rinse your sponge or cartridge out in used aquarium water to maintain your beneficial bacteria for bio filtration. Another note about the HOB filter is that they are far more efficient as bio filters if used with a sponge pre filter such a filter max.

For larger aquariums a combination of a canister filter and an internal filter for cross circulation (I recommend Eheim, Via Aqua, Jebo- I do NOT recommend Fluvals as they have poor head pressure, high flow by rates and an un-reliable impeller).
Other filters of note include the wet/dry, under gravel, and fluidized bed.


Most tropical fish do well at a temperature between 76 and 80 degrees Fahrenheit. (Discus prefer warmer).
Goldfish do not need a heater.
I recommend 25 watts for every 10 degrees of ambient temperature you need to raise your aquarium temperature. EX: If your home is 68 degrees and you have a 40 gallon aquarium, to reach a temperature of 78 degrees you would need a 100 watt heater.
Also remember that bettas are still basically tropical fish too, so if they are kept in a bowl try and keep them in a warm area of your house, preferably above 70 F.
A light does not pass for a heater, you cannot leave your light on 24/7 (an exception would be an Infrared reptile lamp, which are great for bettas).

For more about aquarium heaters, please see this article in my Aquarium Answers Blog:
Aquarium Heaters; Preset vs. Non-Preset


Your aquarium will not be at peak biological filtration for 6 weeks (or more). To start your biological filtration, there are many cycling products available, such “Cycle” by Hagen. My success with these products is mixed at best; it is very difficult for the aerobic bacteria that are needed for cycling your aquarium to live in a sealed container kept at room temperature, as they die very quickly without oxygen.
I prefer to add gravel and/or used filter sponge or cartridge from another aquarium.
This method of adding media is much faster (you still have to take it slow), and provides all the necessary bacteria, the only negative is adding disease pathogens to your aquarium, but I have rarely encountered this problem.
If you add plants (many such as hornwort remove nitrogenous waste), you can stock somewhat faster as the plants will remove ammonia too.
We used this method for our Aquarium Maintenance route for years and never lost a fish to Ammonia or nitrite poisoning.

Another method is fishless cycling where un-scented ammonia is poured into the aquarium (3-5 drops per gallon pure ammonia) so as to bring your ammonia level to 4-5 ppm. Then it takes about 3-8 weeks for the aquarium to cycle. Although this method is growing in popularity, I do not recommend it, not because it does not work (it does), but because human nature is to want to add fish sooner than the 3-8 weeks it takes for this method.
The method of adding media is much faster (you still have to take it slow), and provides all the necessary bacteria, the only negative is adding disease pathogens to your aquarium, but I have rarely encountered this problem.

This is just a small snip of my full article about freshwater aquarium basics, for my full article with more information including:  Aquarium (choosing the right aquarium for your FW Fish)• Substrate (Gravel, sand)• Filters
• Heater• Water Conditioning• Cycling• Live Plants• Fish Acclimation
• Feeding• Cleaning• Chemistry (& Test Kits)• Smelly Water• Green Water (from algae)• Cloudy Water; Please visit this URL: http://www.americanaquariumproducts.com/Basic_Aquarium_Principles.html

Professional aquarium maintenance experience since 1978 as the owner of one of the larger aquarium maintenance companies in LA, CA.

I have been in the hobby since 1969.



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