Looks like mechanical damage from here, I'd forget it. Sounds like a lot of water, even for gritty mix. A lot of fertilizer too (I'd suggest too much, that's why it's so fat & plump as you said). Personally, if it were mine, I'd use a smaller pot. Unless the roots are huge, it's not good to have so much empty mix (assuming that's what's under the rocks). Some succulent growers use little to no fertilizer, feeling it's both unnecessary & makes for overly lush growth. Tho' I grow indoors only, my Aloes are in West window & I only fertilize them once or twice a year, in Summer only. Anyway, back to the damage, it looks like maybe it was bent against the edge of the pot, or a nearby one, looks mechanical (& not spreading) to me. I'd only be concerned if it somehow spreads.

Norma, I'm really frustrated with this as well. Here are a few photos of A. petricola that I bought last year from Arid Lands. Bob Web acknowledged that particular plant had been treated with a systemic for aloe mite (cancer) and that it was cured of the disease. He offered me to return the item; but I decided to just toss it; $12 plant wasn't worth it. You're absolutely right Norma, they should never ever sell damaged plants. In my case, they had known of the problem and they still mailed them to me (this was my first order from Arid Lands). My latest order from Arid Lands, of course, to my surprise had cancer scarring (photo above). This time, I emailed them before I placed the order to insure that they check my plants for any mite damage and not send ones that show any scarring. I felt that they were a little taken aback by my request and they ultimately agreed. Well, you know the rest of the story. As a side note, I had ordered a 1 gallon plant and got a 4" size identical to my other 4" size plan (same species). I sent them the photos of the 2 identical 4" plants and asked for the appropriate credit; but they refused and mentioned "prices are fixed", that I could return the plant and get a refund that way! So if Arid Lands is listening (I am sure they are), my suggestion to them is never sell these damaged plants to customers. Period. It doesn't matter whether the plant is presumably cured of the disease - JUST DON'T SEND THEM in those conditions. -j

Using any broad spectrum poison to control any insect pest is usually a waste of time, energy, and money since that same poison that kills the pest will kill off any predators that could aid in control which allows the pest to come back undisturbed and grow with greater damage. Predators, such as the Stethorus beetle, can be a help although Spider Mites are fairly easily controled with misting which raises the humidity around the plant which slows their reproduction. Pest control is not a one product thing but is best approached with several widely divergent methods.

Nik - Glad to see your other thread got some traction and hopefully results! If you haven't cut off the distorted growth on your cacti, I would do so. The pests really like to hide in the crevices and even inside growth masses (often they have internal folds). Stush - Thanks for your input. Many mites are host-specific as you say. Eriophyid (Aloe mites) are probably the scariest thing I've ever dealt with. There don't really seem to be many success stories or solid advice out there, other than destroy/discard the plant immediately. Plantspace - Yay, thanks! It does appear very grim online and these plants were so hard to get. I couldn't give up on them so I did a crazy amount of research instead. Here is my Ultrasonic Cleaner. It's capacity is 600mL, which is a decent size for small plants. You can get bigger ones, but they cost more than $40. If you are curious, there was a really good study by the Agricultural Research Service, U.S. Department of Agriculture: Ultrasonic Treaments to Control Surface Pests of Fruit. The reason I went for ultrasonic miticide application are as follows: Ultrasound destroys mite tissues and kill them (10 minutes+ bath). Ultrasound knocks the mites off the plant and many of the eggs too. Full immersion of the plant in miticide ensures full coverage. Ultrasonic agitation enables the miticide to penetrate deeper into crevices where mites like to hide. Ultrasound cleans debris from the plant, making further close inspection easy. My ultrasonic miticide application method: Bare-root the affected plant. Put the plant upside-down in a small glass jar or beaker. This saves the amount of miticide necessary and keeps the main bath clean for other things (jewelery, etc.) Mix the miticide of choice in a separate container. Warm water is better along with a little surfactant or insecticidal soap. This improves cavitation significantly. Place the small jar with plant in the ultrasonic cleaner. Fill the small jar with miticide up to the bath fill line. Try to not have any bubbles in the leaves. Use a metal chopstick or similar to move the plant around. Fill the main bath portion with warm water. Make sure you don't fill too high or else the jar and plant will float up. Run the ultrasonic cleaner for 10 minutes for maximum effectiveness. Once done, set the plant to air-dry and then repot. Leave out of bright light for a week and then reinspect. The biggest risk that I was worried about was phytotoxic damage from the ultrasound to the plant. It was a non-issue. Based on scientific studies, the ultrasound does not penetrate deeply into the plant tissues so they are not damaged. In practicality, some of the finer root hairs are probably destroyed in the process, but overall I saw very little difference. The leaves all looked and grew fine after the ultrasonic treatments so I don't think there is much to worry about. The miticides I used were Avid, Bayer 3-in-1, and Schultz Insect Spray (Insecticidal Soap plus Pyrethrin). This was extremely effective. For future mite treatments, I would also consider Floramite and Sevin for rotational purposes. I have more import buys currently on their way. =) My biggest frustration with these plants is that I paid for phytosanitary inspection and certificate, yet the plants never came with the certificate and were not clean. So I am doubtful it was done properly. For any new additions, I always inspect carefully with a loupe (sometimes microscope) and quarantine if I am suspicious of anything. A watchful eye has been the most important asset of mine.