Seedling Check: Aquarium Water Fertilizer

Last weekend I started some tomatillo seeds. These plants get big and bushy and are quite prolific, so we only have three plants in our garden plan. I planted three seeds each in three yogurt cups to hedge our bets:

They are in a black cake pan to try to give them some extra heat, since tomatillos need really warm temperatures to germinate — even at 75-80 degrees, it can take two weeks for the seeds to sprout. Nothing is going on yet, but that's not surprising since our indoor temps are likely around 65 degrees, and maybe 70 in that window on a sunny day. These seeds aren't exactly new (maybe three seasons old?), but we store them very carefully in an airtight container in the back of the refrigerator, and that has served us well for saving seeds in the past. Hopefully this is just a matter of being patient for another week or so. 

The rest of the seedlings are doing well. The leeks we started two weeks ago have sprouted and are stretching up to the sun:

The onions, broccoli, and cabbage are also looking good:

So good, in fact, that most of the broccoli and cabbage seedlings have their first set of real leaves. We planted them four weeks ago today, and with their cotelydon leaves starting to fade away, it's time to give them a little bit of fertilizer. Fertilizing seedlings is somewhat controversial, because they are sensitive and easily burnt. After some research on the subject, I decided to give some of our aquarium water a try as natural fertilizer for them. Plus it's free, thanks to Poppy:

When I change the water in the aquarium, I scoop out about half every three to four weeks (I'm not the world's most doting fish owner, so it's a good thing that bettas are tough). That filled up about half of a pitcher with nutrient-rich water, and I filled up the pitcher the rest of the way with warm tap water to dilute the solution for our seedlings. Then, each cell in the flat that had seedlings with two real leaves got a teaspoon of the aquarium water solution to fertilize it. I plan to repeat once per week, depending on results (I'll obviously stop if it kills them).

With using just tiny amounts, there's plenty of aquarium water fertilizer left over to use in the weeks between water changes. As you can see, I labeled the pitcher to avoid a hilarious but horrible-tasting mishap. My only storage plan for that water is to keep it right there on the bench with the seedlings...hopefully it doesn't get gross as it sits in the sun. This is all yet another experiment, so I'll keep you posted on how it goes.