The answer to "why" is anaerobic bacteria activity - no aeration.

Al

Most commercial potting soils are not free-draining enough. I always mixed my own soil when using self-watering containers. I added a lot of perlite to my mix, even more to the mix that I placed at the bottom of the container. And I also mixed in a handful of charcoal with this soil, to prevent "frogginess."

If I were you, I'd repot with new soil amended with some perlite. And I would water less until the okra fills more of the pot with roots.

I use H202 on my plants, about 1tbsp per gallon, though I manually water. Reposting sounds like a good idea but a little peroxide probably wouldn't hurt, and would take care of the anaerobic bacteria for sure.

I would agree it sounds (smells) like lack of aeration. I am not a fan of the Wal-Mart units that I have seen as they aren't always very well designed (they have been a mixed bag, some are OK).

The Gardener Supply and Earthbox units provide for good aeration.

If you are using a heavy potting soil instead of a mix that would also explain it. The potting soils do not usually perform well in containers, but certainly not in self waterers. You really want a peat based mix (minimum) or better in a self waterer. Adding some perlite or other media also is desirable if it's a store bought mix as they typically don't have a whole lot (10% or so).

I have found the Miracle Grow potting mix to be of variable quality (OK to awful) and it seems they use whatever is on hand rather than maintain consistency in the product and their potting soil belongs in raised beds, not containers.

Im using two sub-irrigation planters from Walmart with my standard 1:1 perlite and peat-based potting mix or pine bark fines with some CR fertilizers and top dressed with a thin layer of compost. Neither the planters nor my potting mixes smell. IÂm, however, not using these self-watering planters as you are or as instructed by Earthbox.

The Misco Wal-Mart self-watering planters IÂm using have exposed and removable bottom water reservoirs. Since I am gardening under semi-protective shelter on a balcony and for various unique and horticultural reasons, I opted not to use and cover the potting mix with plastic mulch during this trial period. My potting mixes in these planters are not protected from Texas downpours and humidity. Under recent prolonged rainstorms and not being able to deliver and retain the necessary fertilizers to correct prior nutritional deficiencies, my transplanted gardenias showed emerging water stress - increased yellowing and browning of the leaves; hence, I also chose not top off the water reservoirs after the first week of use. A few days ago, I relocated the pots to let the potting mix dry out between rains to facilitate the movement of oxygen to the roots more efficiently and only filled the reservoirs partially with a weak acid-loving fertilizer solution. Any visible progress was slow. Instead of risking damaging the roots by watering and delivering the needed soluble nitrogen and micronutrients to the potting mix and the roots or further delaying supplementing the needed fertilizers and micro-nutrients until the potting mix moisture is ready, I also made due with a temporary weak concoction of acid-loving fertilizer foliar spray. The temporary foliar spray made a quick visible difference. The two gardenias have stabilized and are both doing well in the Wal-Mart sub-irrigation planters and with empty and partially filled water reservoirs. I project based on my short-term experience of using the Misco sub-irrigation planters so far with my fairly light mix and under my current wet growing conditions, topping off the water reservoirs may only be necessary periodically during vacation or hot and active growth periods in mid-summer growing conditions.

Odor invariably has to do with soil moisture control and air movement. The wet rag smell is due to poor aeration, which can be caused by many factors such as, waterlogged growing medium, overpotting  little or no water and air movement due to reduced plant respiration and transpiration, emerging bacterial/fungal population, the use of plastic mulch for the wrong plant, climate/zone/season, or on the wrong SW planter, stale, unmoving, under-utilized water in reservoir over prolonged period of time, or any combination of the above.

In theory, all passive sub-irrigation planters, small or large, closed or open, and without the use of air and water pumps, work off the same principles. Unless a design violates and neglects some physical laws in a major way, any differences in the effectiveness between planters should not be significant enough that they can't be easily accomplished in another way or managed by proven horticultural practices. Moreover, any advantages over hands-off effectiveness and good designs of one sub-irrigation design over another may be neutralized and less essential as in meeting the diversity of growing conditions and horticultural needs of different plants. In any case, itÂs more economical and effective to increase soil aeration (and/or the effectiveness of capillary action) by modifying the potting mix directly rather than shopping for the best sub-irrigation planter. Even if one has the best passive sub-irrigation planter on the market, the composition of a potting mix is still a leading consideration with respect to the needs of the plant and specific unique growing conditions.

Other than the viewable exposed water reservoirs (an advantage or disadvantage depending on perspective) that may compromise the health of roots in extreme micro-climates and temperature fluctuations, or may subject them to attacks from insects (not an issue yet in West-Nile country Texas but the opening can be covered or insulated), I kind of like the simplicity, the functional flexibility, and the prices of WM's welf-watering planters, especially when the same laws of physics apply in all passive sub-irrigation growers. While there has been a lot of intervention on my part with this current semi-open sub-irrigation setup exacerbated by frequent downpours while trying to correct certain nutritional deficiencies in the first few weeks of this trial period, I am satisfied with the progress made by my gardenias in the Misco Self-Watering Planters. There is some appeal in branding a method or a planter as hands-off user-friendly, but my primary interests in using sub-irrigation planters and hydroponic systems in gardening are not for hands-off benefits but to be surrounded by nature, eat clean nutritious foods, grow things well with less efforts and higher yields while conserving resources  water and fertilizers to reduce environmental pollution. There is no buyerÂs remorse so far, but without testing the planters over at least one summer and winter and in other pot sizes, itÂs still too early to reach a verdict about the value of the purchase or future purchases.