The tank is ten gallons ,and 5 months old, two months of cycle, three months stocked. Filtration is one Aquaclear 20 filter and one Rio 50 powerhead. Livestock One neon goby, one fighting conch, four blue leg hermits, four red leg hermits, and five turbo snails and what ever is on my LR. 15lbs of LR, 30 LBS LS. I change the water once a month, about 2 1/2 gallons at a time. I started with Tap, but now use RO water from the store.
First of all, what are these crabs and snails eating? IMO you have way to many of these guys in your tank. I did the exact same thing as you did, way to many of them and there is not enough natural food for them to all eat.
Secondly, I also did what you did. Water changes once a month just will not cut it in a 10 gal. "Been there and done that" Disaster.......
With this 10 gal you must do weekly water changes to keep everything in check. Also remember that you have 10 gal you are dealing with.
A pair of perc clowns or a firefish and a small clown goby would be very nice but no more. I would also have just one hermit crab and one snail in there.
In my 25 gal I have one very large turbo snail, one blue leg hermit crab and one algae eating cowrie. That is it, this is my test to see how long these critters can live for. So far it has been 6 months and all is well, no algae in the tank anywhere.
I just about die when I see how many snails and crabs people put into their tanks. My question is "What are they living off of".
As for your conch I cannot comment as I don't know anything about them.
Glad to see you are using RO water....
The Aqua Clear Filters are great, I have two running on my 25 gal. So your filteration is just fine but since you have the neon gobie in there and if you want to keep him I would add just one other fish that is not a big size and that would be about it.
Good luck.....