Backyard Aquaponics
A place to discuss aquaponics

Hi guys, is there a specific flow rate in your bio filter that helps it produce nitrites in the water or is the water flowing in and out the filter enough. Thanks in advance for all the replies and advice. Tonille

For the purposes of most people, having the water flowing in and out of the filter is enough. It is possible to have too high or too low a flow and there probably is an optimum for nitrification. The bacteria are pretty durable though so unless your flooding the filter so fast it's slamming everything around (which might cause attachment problems) or so slow it's barely flowing (which might cause low oxygen levels) you're probably OK.

Ok well my system goes as follows: I have a fish tank with a pump that pumps 1800l/h into a 25lt bucket which then drains into my grow beds. The pipe from my fish tank is a 15mm pipe and from the bucket to the grow beds is 20mm. I am still trying to figure out the flow from the pump as it pushes my bucket lid off so this wknd I'm planning to add in a ball valve in between the pump and bucket as to slow it down a little bit.

Take some of the flow and direct it back to the fish tank for aeration using a T (if you're not already), that's what most people do. That can also be used to direct the flow around the fish tank so it self cleans better. You'll still need a ball valve though.

I was thinking of opening the ball valve a lil so it flows in to the fish tank as well as my grow beds draining into my tank. My main concern is that there isn't enough flow to make nitrites in my filter causing my plants to not grow to their potential.

Water flows and retention times through the grow beds can work in a wide range. What is perfect is too hard a question to answer because all systems are different. Whats more important is to turn your FT volume over approx once per hour, then trial small adjustments to suit your system design for the plants.

Welcome to the forum!

Are your grow beds media beds? If they are, most of the nitrification will be happening in there. You don't need a separate filter for nitrification unless you're running a system with little or no media, like all deep water culture or nutrient film. Most setups that have media beds and a filter are using the filter to remove solid wastes.

Are you testing your water? Low nitrate levels (nitrates are the ones you want for the plants, ammonia and nitrites are the ones you don't want as they're harmful to fish) might just mean that your plants are using it all, not that you're not getting any formed. Other reasons for poor plant growth could be nutrient deficiencies, like iron or potassium etc. Do you supplement? How old is your system?

Post some pictures! We like pictures! And if your plants are showing symptoms of nutrient deficiency then someone here can probably help diagnose what they need.