Switching Out Sand For More Plant Friendly Substrate

I currently have pool filter sand in a 50 gallon community tank with lots of live plants and would like to “upgrade” to a more plant friendly substrate such as Aqua Soil. My current pH sits at about 7.2. I just set up a 15 gallon with Aqua Soil and see that it’s keeping the pH around 6.0-6.2. That is a drastic difference. I know how to do a substrate switch but I’m not sure how to go about re-acclimating my fish. Inhabitants are: 10 harlequin rasbora, 7 sterbaI corydora, 1 Siamese algae eater, 4 platy plus about 10 fry (all of the platy are going to a new home soon, preferably before the substrate switch), 2 Amano shrimp, 1 ghost shrimp and 1 mystery snail. I have an empty 26 gallon that I’m going to use for (very) temp housing while I switch out the substrate. I’m also upgrading to a Fluval 406 canister from a Marineland HOB.
The acclimation is what scares me. Is there a better substrate to use for this type of upgrade? Is there a good process to use if there isn’t? Please share your knowledge and experience! Picture of the current setup included.

 

Do you know how fast the ph drops, and your current KH? If it takes more than a couple days I think putting them right back in after the switch would be okay.

 

Wouldn’t the sudden change in pH stress them? My tap water pH is around 7.6. I did a water test a few hours after setting up the tank and it was 6.6. Yesterday is was 6.0. I’ll test again later this afternoon and I’ll check the KH as well. Sounds like I may need something to bring the pH back up a little before I put fish in this tank too.

 

Oh darn, I forgot to mention that if this is an ADA aqua soil it'll leech ammonia for a while. I would keep the fish in the spare tank for a few days until your filter catches up, or you can do daily water changes, and then add them in once ammonia is no longer an issue. I don't think the drop will be an issue, after all shipped fish end up in different conditions as well. You can drip water from the soil tank into the temp tank to acclimate them back.

 

Yes, I did get an ammonia reading right away in my newly set up 15 gallon but I wasn’t sure if it was from the Aqua Soil or the dirty sponges I threw in the filter to seed the cycle. I did a water test just a few hours after filling the tank and had that ammonia right away. I’ll have to lol into this some more. I don’t have my heart set on ADA. Fluval makes a good plant substrate as well as Dennerle. Do you happen to know much about either of those?
I really wish I’d never put that pool filter sand in there in the first place.....

 

Yes, I did get an ammonia reading right away in my newly set up 15 gallon but I wasn’t sure if it was from the Aqua Soil or the dirty sponges I threw in the filter to seed the cycle. I did a water test just a few hours after filling the tank and had that ammonia right away. I’ll have to lol into this some more. I don’t have my heart set on ADA. Fluval makes a good plant substrate as well as Dennerle. Do you happen to know much about either of those?
I really wish I’d never put that pool filter sand in there in the first place.....

I believe they're not quite as nutrient rich as ADA, but also don't leech ammonia. Fluval's has a slightly lesser ph buffering effect too I think, maybe around 6.5, from what others have said.