Lettuce growing very slowly; brown spots on leaves

[Dennis Jay]

My system has been fully cycled for six months, but still not getting good growth out of most of my plants. Any suggestions would be welcome.

The system:

50 juvenile largemouth bass in 330 gal tote.

12' x 2' x 12" grow bed with hydroton, cycling every 18 minutes.

System is inside greenhouse with grow lights.

Water tests are pretty consistent with pH at 6.5; ammonia at .25 ppm; 0 nitrites and nitrates at 160 ppm

Temperature stays between 60 and 70. Higher on sunny days.

Humidity is high at 80 to 85%

I add a bit of liquid iron and potassium about every two weeks.

The problem:

30 days ago I planted lettuce seedlings. They grew for a couple of weeks and then very little growth since then. Some leaves died off. Others have brown and black spots (see photo). At the same time, I also planted a few seedlings in dirt. They are now about double the size of the lettuce in the grow bed.

Thinking that the lights might be too harsh on the plants, I moved them up to about 18" above the plants. I'm also thinking that there may be too many solids entering the grow beds (even though I have several hundred red worms), so I began filtering the water.

The fish are doing great, and they've about doubled in size in the last 60 days.

Anyone have any ideas? Thanks.

[Jon Parr]

Indeed, be careful about using H2O2 or any dissinfectant in AP, of course. But in order to harm your bio filter, it must reach your biofilter as active H2O2. If you dump a whole bottle of hardware store 3% in your grow bed, the H2O2 will kill single celled organisms indiscriminately as it disperses through the system, leaving in it's wake a sterile pathway. Big deal. If it doesn't wipe out the whole system, the system will recover, probably without hiccup. That can't be said of any other disinfectant. The truth is that H2O2 is very short lived in an abundance of bacteria, as the bacteria it kills robs the extra O, and leaves behind H2O. Of course you can do damage, but it is a very mild risk for the benefit it carries. If your media is dry for 2" like it's supposed to be, then you can fog the plants and surface liberally (use your noggin), and the H2O2 won't make it to the fish or the biofilter. I do it all the time.

The fact is that spore carry the problem to other areas, and stick around to cause problems again, and H2O2 kills spore. It doesn't kill the fungus, it doesn't kill the plants, it doesn't kill insects, but it does kill spore and bacteria. If you really want to impress your friends, use a cap-full of H2O2 for the first watering after you plant seeds. It will kill any spore and bacteria immediately surrounding the seed, and rapidly quicken the softening of the hull, cut germination times in half, and increase germination rate. It may even fix your infected seeds, IDK. 

Yes Bob, 1 1/2 to 3% can be put straight in a spray bottle, and is a good disinfectant to use for your garden tools, cleaning pumps and hoses, test equipment, fish nets, etc. 

Don't let any go straight to the fish tank, as there are far fewer bacteria to sacrifice before it hits the fish's gills, which could be lethal.

Roger said:

I'd watch out using H2O2 in your AP system.  It is a disinfectant that will kill that bacteria in your bio filter.  If you do use it try to cover the top of your GB so none of it enters your AP system.

[Jim Fisk]

Another great thread. You guys rule. Truth about Forums is that all the info in the world means pretty much nothing until you run into these problems and then the light goes on in your (read mine) head when you need it. I learned more in the few min it took me to read thru this thread than in the past month (at least) regarding GH AP.

I was ready for this thread as now I am running into the dreaded GH scenarios of which there are sooo many. Basically you are saying to treat the GH as a "clean room". I have purchased many seedlings and now I AM SCARED

I have a whole gal of food grade H2O2 so I will add that to my list...

[Jim Fisk]

OK, why does my reply get truncated? about half is being tossed away. Anyone else experiencing this or have I reached some sort of limit? Strange. I have retyped it all over again and once again it got cut in half. I'm done.

[Jon Parr]

Yeah, Jim, most of my comments on this forum are from my iPhone, and for some reason it gives me trouble now and then, not with chopping in half, but just won't post. So I copy and paste the comment to "notebook", and try again later (that is if I remember to)

GH pest management has three strategies, and which is best is really open for debate.
1- intentionally low pest security, meaning wide open large screens for honey bees, pests, and pest predators. This works pretty good for lazy folks like myself, especially if you are planting beneficial plants to attract the predators. No fuss about pollination, and no big concern about sterilizing everything.
2- moderate pest security. This one is fine for new greenhouses, and light traffic GH's with cleanly guests. Once a pest gets inside, though, trouble trouble.
3- high security, meaning positive pressure and HEPA filters, thrips screening, humidity and temp control, haz-mat suits and dissinfect routines. Just the thought of all that work spoils my mood, but is probably the smartest long term plan for commercial use.

I'm a low security type guy. Address the pest directly. Mold? Increase airflow and temp, decrease humidity. Spider mites, fungus gnats, white flies, aphids? Allow predators, spray with tea, nuke them with CO2. Nasturtiums are awesome for the garden by the way; trap crop or aphids, pest predator magnets, repel white fly and spider mites. Yep. And borage, and multicropping.

[Jim Fisk]

Great advice as always Jon.

So today I installed the fan, finally got around to cutting off the stand pipes on my first 3 ibc gbs (that I foolishly glued before I knew better, Used a dremel with a cutoff wheel) so as to keep the surface gravel dry, and removed all sick or infected plants and burned them in the gh woodstove (handy new use) and just plain feel better about saving the gh. This thread got me moving so kudos! I will start employing all the other great advice in this thread tomorrow. (well almost all)

Jon Parr said:

Yeah, Jim, most of my comments on this forum are from my iPhone, and for some reason it gives me trouble now and then, not with chopping in half, but just won't post. So I copy and paste the comment to "notebook", and try again later (that is if I remember to)

GH pest management has three strategies, and which is best is really open for debate.
1- intentionally low pest security, meaning wide open large screens for honey bees, pests, and pest predators. This works pretty good for lazy folks like myself, especially if you are planting beneficial plants to attract the predators. No fuss about pollination, and no big concern about sterilizing everything.
2- moderate pest security. This one is fine for new greenhouses, and light traffic GH's with cleanly guests. Once a pest gets inside, though, trouble trouble.
3- high security, meaning positive pressure and HEPA filters, thrips screening, humidity and temp control, haz-mat suits and dissinfect routines. Just the thought of all that work spoils my mood, but is probably the smartest long term plan for commercial use.

I'm a low security type guy. Address the pest directly. Mold? Increase airflow and temp, decrease humidity. Spider mites, fungus gnats, white flies, aphids? Allow predators, spray with tea, nuke them with CO2. Nasturtiums are awesome for the garden by the way; trap crop or aphids, pest predator magnets, repel white fly and spider mites. Yep. And borage, and multicropping.