Hermit dies after molt

I had this hermit crab for about a month or so. my tank had massive algae bloom all around. after a massive rearranging of my LR along with a 20% water change, he molted that same night. ever since the molt his movement has gone from 80% ( because when he eats he doesn't move) to 2%, even 0%. when i move his shell he would barely move to retract. after a week of this behavior, he died.
as for water conditions, nitrate was steadily decreasing since i did a little algae cleaning from 50 to 25 (haven't checked last week). ammonia=0, nitrite=0, ph=8.0, salinity=ranging from 1.024 to 1.026, temp=28 to 30 degrees C.
any possible causes you guys can think of? i'm planning on getting more hermits cause they're fun to watch. there's a shop that sells one regular hermit kept in a very shallow tank for about less than 2$, while some street vendor (no stall) sells one kept in a basin with almost no water(not sure if fresh or saltwater) for about 1/5 of the price from the one from the shop. i just wanna get the cheap ones but not sure if they'll last long under deep water. they definitely look the same, but i heard there are land hermit crabs. i wouldn't know the difference though unless they're both kept under deep water.

 

50ppm nitrates are plenty enough to kill inverts (including hermits), specially when you figure in that they are probably even higher, and your algae is masking it.

 

Thats probably it 50ppm is super high. BUT one thing to remeber is who knows how old that hermit is when you got it. Honestly, it could have been nothing to do with anything in your tank but a natural death. I think people forget about the natural death cause in this hobby, but in ur case im sure the 50ppm had something to do with it.

 

Yes 50 ppm probably has something to do with it. Why don't you go to a reputable LFS and get a couple scarlets and blue legs so you know they're healthy.

 

50ppm of nitrates is not considered super high, anything below 60ppm is considered "tolerable." 40ppm is considered a normal tank for the most part. Obsessing over 0ppm is something that hobbyists are generally guilty of. After I learned more about this hobby, the less I worried about my nitrates. I still test for them weekly mind you. Obviously reefs are more delicate and lower nitrates the better. The fact is, many reef corals will use nitrates as a source of food, and that naturally lowers the tank's nitrate level down to near 0ppm. Personally, I don't think 50ppm of nitrates killed the hermit, though it may have weakened it. Moving the rocks and sand will cause the detritus nasties that have settled to become free floating. Bacterial colonies could have infected the crab since it went through a molt, which is when they are most vulnerable.
I have a maxima clam in my tank and it helps keep my nitrates down at about 5ppm, along with my refugium. Before my clam, I was at 15ppm with only my fuge. If you have proper lighting and stable system, meaning no NH3 and no NO2, a clam is something that will help keep your nitrates under control.