A Community and Forum For Aquaponic Gardeners

To filter or not to filter, that is the question...

I'm currently in the process of building a larger system but am very new to AP. If the plan is to add worms to grow beds I'm thinking that any particulate filtering needs to be "post" grow bed not pre or will I even need to filter if I am hoping to run flood & drain beds with a bell siphon?

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Permalink Reply by Cris Meeks on February 9, 2016 at 2:53pm

Thanks for the clarification George. That would be pretty easy to accomplish with something like a swirl filter in a larger system. Right now my largest is a 30 gallon & I'm thinking something like a canister poly pad to handle the job. I'm curious to find out if Jeff S' smaller systems are filtered. It makes sense that the higher the stocking rate and the larger the system the more impact that filtering would have.

George said:

When solids are removed post fish tank, they contain nutrients. Sometimes those solids are drained to another container and aerated, then allowed to settle and the water is pumped or drained back to the aquaponics system. This is referred to as mineralisation. It's a way of removing the nutrients from the solids and keeping them in the system.

Usually, the solids are drained off the filter and used in soil gardening, especially if the system is heavily stocked and has a nitrogen surplus. In this situation, there is no concern for keeping all of the nutrients in the system.

However, when a system is new or lightly stocked, it's important to keep the nutrients in the system.

Cris Meeks said:

please explain what you mean by a "mineralisation step"?

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Permalink Reply by Cris Meeks on February 9, 2016 at 3:37pm

Okay, so I'm coming at this more from the aquaculture side (and as a practicing veterinarian) and there are some species such as tilapia & bettas that can tolerate more nitrates than others but the key word here is "tolerate". Nitrate levels over 50 ppms can damage kidneys, liver, nervous & immune systems. It reduces the slime coat that helps the fish ward off infections & impairs what immune response it can make when that infection gets through. It will kill invertebrates like crawfish, snails & shrimp pretty much outright. Don't let anybody tell you that nitrates don't affect fish...it's just not true.

Jeff S said:

Nitrates don't particularly affect the fish, or so I've been told. Mine seem OK.