1.1.12. How to Make Fish Thrive

There was some aquarium advice on Facebook from one Sean Dwyer which I think was excellent:

Great advice!

The simple fact is that Mother Nature is very forgiving and very flexible. One can set up an aquarium, add some water and some fish and be very successful from the get-go. There is only one “rule”:

If your water has chlorine in it you must condition the water to remove the chlorine

Beyond that, there are NO “rules” or “requirements”.

Making Fish Thrive

But all hobbyists want to make their fish healthy and “thriving”. Five parameters are key to achieving that.

Note that these five things together should produce crystal clear water. Crystal clear water has a very low bacterial count in the water. Crystal clear water indicates conditions which where fish will be very healthy.

Let’s put these items in a table and score them, zero being non-existent and ten being very well maintained.

Item needed for fish to thrive	Score
Excellent biofiltration	0-10
Light feeding	0-10
More than 45% protein food	0-10
Good water aeration	0-10
Filter rarely lightly cleaned	0-10
Total score	0-50

The cumulative nature of these guidelines has led to things like “I know someone with Africans and only cartridge hang-on-back filters”. Yes, if everything else is perfect one can keep Africans with cartridge hang-on-back filters (these filters are notoriously poor on biofiltration). Just don’t try it with an Oscar. The Oscar will die from hole-in-the-head with a cartridge hang-on-back filter as the sole filter the majority of the time.

These are only rough guidelines and far from “rules”. They are violated all the time quite successfully. We go into each point in the discussion below.

Have Excellent Biofiltration with lots of filter media surface area

Biofiltration is dependent on something called “effective surface area”. It is the number of square feet of surface area available on filter media where beneficial bacteria can grow, Note that when it comes to the media in a filter the “EFFECTIVE surface area” is often much less than the advertised surface area … MUCH less.

Cartridge filters, both internal to the tank and hang-on-back varieties, tend to be very poor filters with very small effective surface areas. Sponge filters, under gravel filters, canisters and sumps have decent to very good effective surface areas.

This is the most important of the five variables. Good biofiltration can overcome a lot of other short falls.

Feed very Lightly (two eyeballs’ worth of dry food once a day)

Beginners often follow the directions on the food can: “Feed what the fish can eat in five minutes three times a day”. This is WAY too much food. A much better guideline is to feed dry commercial fish food at a rate equal to the volume of two eyeballs per fish once a day. If you have six fish that is twelve eyeballs worth of fish food.

Feed Food with a protein level over 45% on a dry basis

Now everyone wants to know what defines a low protein food. I make the cut-off at 45% for dry commercial fish food. But the “45% protein” level is completely arbitrary. In truth there is a continuum between 30% and 60%. A level of 42% protein in the dry commercial fish food won’t be “ideal” but it also won’t be that bad. The key is the clarity of the water. Is the 42% protein food giving crystal clear water? Or is it giving “dull” water or even slightly cloudy water. There is a “threshold” here.

But where the threshold will be is very dependent on a multitude of variables. For instance, 34% might give crystal clear water in one aquarium setup while 52% might give “dull” water in another aquarium setup. Note that if I must buy commercial fish food, I ALWAYS buy the highest protein level I can find.

Have great aeration of the water

There are two ways to get great aeration. Air stones with a larger sized air pump will provide good aeration. And a wavemaker or filter outlet that makes a lot of “choppy waves” also works very well.

Infrequently clean the filter while leaving a lot of brown gunk

The brown gunk in a filter is on the order of 85% of the beneficial bacteria in the aquarium. Clean it all out and the aquarium typically needs to be recycled. So one needs to lightly clean a filter when the flow slows down or stops. Some of the brown gunk should be left behind. If it is a cartridge, only clean off the brown gunk on the face of the cartridge with a small brush.

Crystal Clear Water

Note that some ask “how to I get water which isn’t cloudy or dull?”. In my experience “over-filtration” is necessary for “crystal clear” water. I define “over-filtration” as using far more media surface area than ammonia oxidation requires. I “over filter” (more than 100 ft² (9.29 m²) of filter media surface per pound (454 gram) of fish, in other words a HUGE amount of filtration) all my tanks to get crystal clear water. I also only clean my canister filters lightly only when they plug up and I never clean my under-gravels or my fluidized bed sumps.

I have not experienced any downside to “over-filtration” other than expense. I’ve got one 120 gallon (450 liter) tank on an under-gravel, a FX6 and a 40 Gallon (150 liter) fluidized bed sump. You can look down the length of the six foot (180 cm) of water and you would think the fish are swimming in air. I do have to impinge my outflows at the surface of the water to keep from creating too large of a current in the tank.

Note I use plastic pot scrubbers and lots of foam inserts exclusively as canister media. And I avoid “polishing filtration” with Polyfil or Pinkie pads as the stuff must be cleaned and changed like once a week. I’m too lazy for that. For more on this go to this link:

6.3. Over-filtration

If you are interested in an example of these calculations on the suitability of an aquarium set-up click here;

1.1.12.1. An Example of How to Score an Aquarium

Parameters Which are not Important

Many very well intentioned and sincere hobbyists will disagree with one or many more of these points. I can only encourage them to read the supporting articles and the supporting science. I know this takes a paradigm shift for many and paradigm shifts are never easy.

Paradigm Shift

Note that even suggesting that all and any of these items are not important is guaranteed to provoke a few very unflattering criticisms from self-appointed social media “experts” (some call these folks the “fish police” or “fish Nazis”). One called this list “stupid and downright dangerous“. But the science in the close to 400 articles on this website says that none of these items is all that important to successful fish keeping.

Unimportant topics in more depth

This website uses a multi-level approach to any subject. The easiest explanation is first and then there are typically a series of more and more complex explanations. In keeping with that methodology, here is a link to more in-depth answers as to why these items aren’t important in the aquarium, with links to even further levels in yet greater depth.

1.1.12.2. Unimportant Aquarium Parameters