Backyard Aquaponics
A place to discuss aquaponics

I am having problems with my plants! My system is several years old and I've never gotten the water right. I use RO water and my system is 400 gal. I grow only greens. My Kale is fine but my lettuce has burnt new leaves and some yellowing. None of my plants have grown well and I don't see a very developed root system. My Swiss Chard has silvering on the leaves. This has been an on going problem. I do supplement with potassium and iron. Since my water test I've raised my pH to 7.

I'm hoping someone can interpret the water test and tell me how to adjust my water.
Steve

Hmm,

Your copper and zinc are pretty high. I'm not sure how that affects your plants but it can be toxic for some fish. Do you have any galvanized metals or copper pipe in your system?

Your nitrates seem low, but not too bad. Is your system well stocked? Are your feed rates in line with your grow bed area?

The biggest things I see is your alkalinity and carbonates are way low, and your pH is a bit low. Higher pH may help your plants absorb nutrients better, but my system runs at 6 - 6.5 all the time and is good.

This single biggest difference I noticed with DWC crops is when I added air stones to the DWC. You need really good DO for DWC roots to thrive.

I would add calcium carbonate or potassium carbonate to raise pH and add carbonates.

Also, your sulfur is very high, no idea why but that is unusual. Your phosphorous is high.

I don't know how these things impact your plants, you could have one excess nutrient blocking others, or lack of DO. I do not recommend using RO water for top off, but that's just me. I know lot's of people do. I prefer rain or tap water. Tap water typically has a range of minerals and nutrients that are good for your system, just eliminate the chlorine / chloramine.

This is NOT my area of expertise, but these are my thoughts.

Thank you very much for the information.

Yes I do have a galvanized fish tank. It is a 165 animal stock tank that I’ve epoxied. I see no signs of the epoxy being breached.

I do not know how many pounds of fish I have. I do have 40 sq. ft. of raft surface sitting under 8 HLG’s QB288 V2 Quantum lights. My fish are fed automatically 3 times a day a commercial fish food. I’ll need to check this but I think 90 grams a day. I filter my water with an AST Endurance bead filter.

Yes my alkalinity is low because I use reverse osmosis water. My well water was so hard with so much salt that Penn State told me the only thing it would grow is sea weed. I was to find another water source. That was not possible so I installed a RO system. I raised my pH to 7. I was keeping water at 6.5 using a calibrated Apera meter. When I saw my test results (I’m not sure what happened) at 5.9 I raised my pH to 7. I just replace my meter 3 months ago.

I do not have a DO meter but I do have 2 Hakko 60L air pumps pumping air into 8 large air stones. It could be a problem?

I do alternate between KOH and ca(HO)2 to raise pH and am usually around 6.5. How should I raise carbonates? I could return to my well water for a few weeks as my make up water but that will really raise my sodium levels.

In January I got back my water test report and I had no potassium in my system. I’ve been adding 15 grams of potassium sulfate every week since then. I knew it would raise my sulfur but everything I’ve been reading says that there doesn’t seem to be a toxic level of sulfur for neither fish or plants.

I need at least 5 gal. of water every day to top off my system. Rain water is just not an option. Besides how would rain water have more minerals than RO water?

Thank you
Steve

The air pumps should get it done, I don't see any problems there. In your situation the RO water seems your only option. You can add carbonates with eggshells (boiled, I hear), shell grit, etc. I put mine in a mesh bag and place them in the system as needed. Also, using carbonates and bi-carbonates to raise pH instead of hydroxides is an option. https://www.amazon.com/gp/product/B0064GZPU4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Thanks dstjohn99 for the information. I will get some bi-carbonate and try it so that I can lower my sulfur. I will also add some carbonates to my system. I still think I’m missing something because my greens don’t do well.
Steve

Could the lettuce be getting too much light or heat and getting burned? It is quite sensitive.

I don’t think so. My lights sit 27” above my rafts. The lettuce doesn’t show burnt tips until later in life. I’m not turning anything white. It’s not only my lettuce but many of my other plants show pale yellow leaves. All the leaves of my impatiens flowers died over a week and fell off.



steve