A Community and Forum For Aquaponic Gardeners

Pre emptive nutrient additions

My direct seeded spinach and Swiss chard are now at the 4 leaf stage in Hydroton. All the water tests are right on the money. Artificial light being applied to extend grow day to 16 hrs. Now I am wondering if I should be introducing seaweed extract to the system, or is it too early? I'll have to wait until I make my monthly trip to town to get it, another two weeks. Also, any ideas which brand to look for etc. Also amounts to use.

0 members like this

▶ Reply to This

Replies to This Discussion

Permalink Reply by TCLynx on March 16, 2012 at 12:00pm

Depending on your fish feed, source water and amount of plants and media. Supplemental nutrient additions are not always necessary so there is really no way to tell some one when, how much and how often they would need to add supplements or if they even really need to ahead of time. There are some experts that would even tell you that to add such things is really turning your system into hydroponics with fish swimming in the nutrient tank.

That said, I've often found that with a new backyard type system, some trace elements are usually lacking and seaweed extract does seem to be a really handy and fairly safe way to handle that. In reasonable doses it doesn't seem to hurt fish and does seem to help plants.

What kind to get. Well in Oz they usually use seasol and in the USA Maxicrop seems to be a good brand. I'm not sure what is available in your area but you want to find the seaweed extract that doesn't really add extra nitrogen or phosphorus. So I generally say look for numbers for NPK that are like 0-0-1 or 0.1-0.0-1.0. Now there are wettable powder type seaweed additives that will likely have a higher nitrogen content so be very careful when using those as they will put the bio-filter under more of a load and could cause ammonia and nitrite spikes.

Is it too early, <shrug> probably doesn't make that much difference. And you probably don't need to rush unless you are seeing signs of some deficiency.

What other things you might want to have on hand to keep the system balanced may include

Potassium bicarbonate (used to buffer pH up when it drops, can be found at wine and brew supply shops)

Garden lime (also used to buffer pH up alternating with the potassium bicarb, other sources include chicken grit/shell grit)

Chelated Iron (might be harder to find but you want something that is only chelated iron since you need to avoid adding excess copper or zinc which are often included in some garden iron supplements. If your source water is high in iron or if your pH stays relatively low this might not be needed so much.)