I've had a well-to-over-stocked, sloppy planted/algaed 37 high tank going 2 years. It's had weekly 50% water changes w/ light vacuum. There are small areas that have never been vacuumed because of the plant cover. Absolutely stable parameters. My water is hard and 8.3 ph out of the tap. lt gets DIY CO2 and dry ferts. I don't use R.O. The substrate is a fluorite/gravel mix.
I recently sold the 3 angels I had that grew to large adults, fought like mad, and ate my neons. I assume they were same sex. Right now I'm down to 5 RNTs, and 4 molly my daughter insisted on. (in their defense, they eat algae constantly and make tons of angel fish snacks), and a thousand tiny/micro snails.
I want to get a school of small cory...panda or smaller. Considering that cory like good water, what would be better for them?
1. Dropping them into this tank w/ 2 years of processed shirt in the gravel? Could I get away with this? A huge plus would be no work and no messing w/ plants. -plenty of waste-breaking-down bacteria already in the house.
2. Pulling everything out of the tank and re-do it with pool filter sand substrate, and re-plant? I'd keep the dirty filter, a little of the old gravel, and all the plants so I don't have to cycle.
-Upside...2 yrs of mulm gone, generally cleaner substrate, possibly better substrate for cory digging?
3. Better idea?
4. Light bulb moment...Drain tank, dig out an area of the gravel and then fill it with PF sand? Good enough?
Will cory eat pin-head size snails?
If I get between 5, and 8 cory, how many males and females? I'd like to be able to observe breeding behavior.