AquaDynamite Koi Filtration: Filter sizing.

Make sure you buy the Aquadyne filter for the lowest end of its carrying capacity. Undersizing is the most common cause of nitrite problems with bead filtration.

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Aquadyne Filter Sizing

Have you ever heard someone say that bead filters "never cycle" and that "they will always have nitrite problems?"

I have. I've heard this from every person who:

Overbackwashes
Overfeeds
Undersized their Aquadyne filter and
Doesn't feed the bacteria the calcium they need.

You need to use Calcoforce. It's a calcium supplement that will give you sparkling clear water, a supported pH and happy beneficial bacteria in your filter. We are hardware people. You can get Calcoforce here.

Overbackwashing happens when people backwash every week. The filter bead cake is in constant flux and never settles down. You should backwash at the very MOST every two weeks, and you should NEVER own a bead filter without an air wash system. If your filter is properly sized for the pond, you should be able to go a month between backwashes.
(Backwashing instructions)

Overfeeding happens when people feed a lot of food several times per day. I feed my fish twice per day. I feed a pretty hearty amount of food. If I fed seven times a day I would feed the same overall amount but I'd divide it into many smaller feedings. If your fish have big bulgey stomachs all the time and the water has high nitrate numbers, chances are you're overfeeding. Feed only what the fish will consume in < 5 minutes. Feed at least twice per day but not more than four times per day. (Diet)

Undersizing of bead filtersrs is really common. I'd RUSH to remind you that undersizing is usually caused by manufacturers; and there isn't a manufacturer in existence that doesn't "stretch it". When the manufacturer calculates the carrying capacity of these filters they do math on the surface area of a polyethylene bead. Then they use the known data on the amount of surface area needed to grow beneficial bacteria per pound of fish. Then they arrive at a laboratory number for pounds of fish per cubic foot of beads. This is odd. And usually overly optimistic.

Some of the variables which degrade these calculations are:

Flow rates,
Amount of food those pounds of fish actually get,
Whether the water is warm, carrying less oxygen,
Whether the water is cold and the beneficial bacteria are metabolically challenged,
The amount of fish poop in the filter contributing to bead bypass.

If these factors were accurately considered in realtime, they might arrive at more conservative numbers for the hobbyists. Confessing these more honest numbers will put a manufacturer at a competitive disadvantage to other filter manufacturers who are willing to lie about carrying capacity. So everybody goes along.

Here are some examples of the various successes I have had personally with the Aquadyne Filter.

I've carried 4000 gallons on a 2.2 cubic foot Aquadyne. I am a confirmed overcrowder and overfeeder.

I've carried 5300 gallons on a 4.4 cubic foot Aquadyne.

I've carried 5700 gallons on a 4.4 cubic foot Aquadyne.

I've carried 30,000 gallons on a pair of 4.4 cubic foot Aquadynes.

I've carried 6300 gallons on the same pair of 4.4 cf Aquadynes.

I've seen 1,200 gallons overwhelm a 0.6 cubic foot Aquadyne.

I've seen 5,700 gallons overwhelm a 2.2 cubic foot Aquadyne.

And so on and so on. So, what I intend to do is give you some numbers in a chart to follow which describe my OPINION about what you should choose in terms of Aquadyne filters.

Pond Volume	Notes	Filter Recommendation
10-500 gallons	A good sponge filter or the Aquadyne 0.6 cf.	I mean it. Tiny facilities can get by with inexpensive filtration. You can't keep big fish, so you don't need a big filter. Sorry to lose a sale but you don't need a hardcore filter. Now, if you like the easy cleaning capacity possessed by the 0.6 - you might make yourself very happy. It's a lot easier than sponges.
500-1800 gallons	Aquadyne 1.1 cf	For less than $200 more than the Aquadyne 0.6 c.f., you can more than double the carrying capacity of the pond and it opens the door to having DynaMax airwash which is more important to the small Aquadynes than it is for the large ones! As your fish grow, you're not lamenting your choice.
1800-4700 gallons	Aquadyne 2.2 cf	The best filter, dollar for dollar, that you can buy in this world. Do NOT make the mistake of buying it without the DynaMax air blower system.
4700-6800 gallons	Aquadyne 4.4 cf	I would trust the lone Aquadyne 4.4 up to 8,000-9,000 gallons - and in applications larger than that, I would surely TRY to let the Aquadyne 4.4 carry the 14,000 gallon system solo. What harm is there in that?
Ponds over 7000 gallons	Aquadyne 4.4 cf	The manufacturer rates the 4.4 to 14,000 gallons, but if you did 14,000 gallons: You would need to have your pump on it's highest setting, you'd need to have quite an efficient water return system, you could not skimp on calcium feeding of the beneficial bacteria, and you would really be pushing your luck. But I'd allocate some money to purchase a 2.2 to run in tandem.
Alternative: Ponds over 9,000 gallons	Tandem Aquadyne 2.2 cf	Here's the ideal solution for the person with a big pond, but under 20,000 gallons. But wait, two 2.2 cf units is equal to one 4.4 cf unit, isn't it? No. It has to do with bead exposure to flows. Two 200 lb men can do twice the work of one 400lb man. It has to do with what they can lay their hands on. ...Tandem installs
Ponds over 20,000 gallons	Tandem Aquadyne 4.4 cf	Here's the ideal solution for the person with a big pond over 20,000 gallons. ...Tandem installs
Alternative: Ponds over 20,000 gallons	Aquadyne 8.8 cf	This is a LOT of filter, and it carries enormous fish loads very very well because of its modified center column, but water passage is the thing here. It can only see 2 inches inflow into the head. On the other hand, two Aquadyne 4.4 c.f. units in tandem have the same bead volume but they can see two inflows from two pumps. Same bead load, twice the capacity. It costs $500 more to do the tandem 4.4's than to do one 8.8 unit. The difference is that you can position the two 4.4 units strategically, and if one of them develops a plumbing problem, at least half the system is working.

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