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I have a indoor 20 gallon tank with crawfish and rosy red minnows feeding into 2 pea gravel growbeds, the full setup can be seen at 

It is fully cycled and my ammonia and nitrites are 0, my ph (which was my first concern until I tested it) is 6.8 (although I tested it the day after I added some sea shells so it might have been lower had I tested it before adding them) and my nitrates are about 80. My Crawfish are doing well and even reproducing and their intended treat (the minnows) are doing good as well.

The problem is that all the seedlings (snap peas that had grown to 8 inches, 1 inch chard, 1 inch cerery, 1 inch onion and garlic chives, and other seedlings as well as strawberry plants that I tried to add later all wilted and died.  It didnt seem to mater if they were surface sprouted like most of the seedlings or deep seeded like the peas so I dont think it was a water level issue.  Some turned dark before they died like the strawberries others just wilted the dried up like the peas.  I am afraid to invest in any other plants until I know what is causing this die off.  Does anyone have any ideas?

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Hi Debra,

The water level in your beds should be 1 inch below the top of the media or alternatively the top 1 inch of media should be dry. Also I've noticed some of the seedlings are being wet constantly which is not good. The roots of all plants must be in contact with water at least periodically per hour.

My water level is about 1-1 1/2 inch below the top of the gravel, only a small area is being sprayed but those plants were actually the last to die.  Some sprouts sprouted on the surface but the roots were growing down to the water alright, the pea seeds were planted at or just above water level and had been doing great before suddenly dying at about 2 months old.

Hi Debra,

I see from your videos the drain lines from the GB's are near to the base of the beds, which looks(appears to be) like about 4-6 inches below the top of the bed. If the drain lines are indeed set at a "close to base height", the water level in the GB's should be lower than the 1 - 1.5 inches. Also the fact that you mentioned the seedlings in direct contact with water were the ones to die last to me is a clue. From here i can't be sure of what i am seeing, but at least we can look at issues, crossing them off the list, to find a possible cause.

BTW, when did you place the artificial plants in the FT?

As you can see in this picture the water level is 1 1/2 inches below the gravel level.  I put the plastic plants in the fish tank right before I planted and put the crawfish in, they are aquarium plants not decoration plants so they should have had no effect on the plants also as I said the fish are all doing fine.  I do not have any worms in my beds and I do not have it on an alternating schedule so my husbands concern was that the water in the bottom might have gotten stagnate despite the flow through.  My husband's other concern is lack of minerals, I am using dechlorinized tap water but dont know what the mineral content of it is, havnt added any minerals or anything as I try to use as little artificial stuff as possible, only use minimum amount of an aquarium declorinizer to prevent the fish from dying.  I planted soon after my tank cycled (amonia 0, nitrites 0, nitrates 40) The plants had all been doing well for about 6 weeks, then slowly over about 3 weeks they all died off, I added the strawberries around week 7 after a lot of the sprouts in the upper level died off, they seemed to be doing fine for about a week, didnt even wilt or anything and were really looking great, then over a week they, and everything else died off.

Hi Debra,

Can you do an updated ammonia/nitrite/nitrate test and post the reading? Also what are your temps? Is you dechlorinator plant safe? What type of light are you using for plants.

You mentioned a concern being lack of minerals. Usually in AP we have the inflow and outflow at opposite ends. The inflow is usually at the top of one end and outflow at the botttom of the opposite end. This ensures that the water must flow through close to 100 % of the media that is in contact with the water. This allows oxygen to be transported to all areas of the media. If oxygen bearing water bypasses media, anaerobic pockets develop there and start competing with the Nitrifying bacteria and could eliminate them altogether. Nitrifying bacteria are responsible for processing the fish waste into minerals for the plants.

In your peas pic, it looks like water goes up half way of the media column. I would try to get it closer to the plant roots, virtually anywhere just below the surface will be fine. If you suspect water becoming stagnant, a simple modification of placing the larger media to the bottom of the GB and the smaller stones layering the top could help. Ideally though you should move the outflow to the base of the GB.

I can do another test Thursday but the last test I did was just this Sunday.  Temp around 74-76 F.  Yes it is supposed to be safe for plants. Just sun light from a South facing window, but the plants weren't looking scraggly like you would expect from a lack of sun. So you think a 1/2 inch space between gravel top and water level would be better?  Obviously the water inflows at the top of the top grow bed but we didnt think it out well on the bottom one had have it coming in at about the same height as it goes out at, unfortunately it would be hard to change that now as it would be hard to lower to out flows, but I have heard that adding worms helps with the breakdown of the waste, could that help here?  If so would I use super worms or red wigglers? Would increasing the amount of water going through help? Or adding at 15/15 timer?

Hi Debra,

Ok, thanks. Yes 1/2 inch would be fine. You can also put the coarser gravel to the bottom this will ensure more water movement there. You can use a length of the same tubing on the inside of the Gb's out flow. Make some slits about 1/2 to 3/4 an inch from the end of the tubing insert it into the existing fitting on the inside of the GB. Curve and then bend it down to about 1 inch from bottom of the base of the GB. It doesn't have to seal the opening but it will be able to direct about 90 % of the flow of water from the bottom. Worms are good additions, but won't help with anaerobic conditions which will eventually shut down the AP system. To increase the height of the water in the GB you can raise the height of the outflow tubing on the outside of the GB. The height of the tubing will be proportional to water level in the GB. The flowrate through the GB's must equal the FT volume of water every hour at least.

When we have time we will try to diagram that out to understand it better, we are thinking we are going to have to lower both outflow tubes which would be very hard to do but I am not sure the inside tube idea would be any easier considering I dont know that there is enough pressure to bring the water up that tube but we will work on both ideas a bit. We will probably get a timer as well, and create more of a flood/drain system. We used aquarium silicon around the tubes but are getting some leaks; it just doesn't seem to hold well even in scored areas, can you recommend a better safe sealant? 

Hi Debra,

Yea that's the trouble with just the tubing. Normally we use a bulkhead fitting and fitted PVC pipes. Pipe would surely solve the problem of directing water from the base GB and on the outside to increase the water level. Silicone is a sealant meant to work between surfaces as a gasket not as a glue to stick surfaces together and certainly for resistance of water pressure by itself alone. A cost effective solution would be to use a male threaded adapter into a threaded female, with the silicone as a gasket on the inside of the GB, although a bulkhead fitting is really the way to go. I think the finer gravel to the bottom of the GB is trapping the water there an could be causing problems. The timer though not necessary may be used but make sure to drain from the bottom of thew GB.

Thank you for your data, I found our what was causing the plants to die and it could have killed my family and I as well, see my post in Basic and Useful info and watch the youtube video I made about it:

Hi Debra,

First off, thank goodness everything turned out Ok. This is a first for me, hearing anything like this ever happening in AP. Thanks to AP because it seems like it saved both you and your family! I hope there are no long term effects for you and your husband and especially where your son is concerned.

So... In the interest of safety...carbon monoxide will kill your plants (and you)...

thanks for sharing

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