GH & kH how high is too high?

I currently have a 20 gallon tank and which I am trying to grow out plants and my food for my goldfish pond. I have a few plants in my tank that are native to my region (vallsnaria, tall hair grass, & duckweed) that I am trying to get established because let's face it goldfish are brutal underwater chainsaws. Unfortunately the vallsnaria and duckweed struggle which I don't understand because they are native to the region and are supposed to be easy grow plants. The plants that are actually in the pond but I am trying to get these plants established elsewhere because like I said underwater chainsaws.

I also have a small population of native bladder snails in my aquarium which thrived in my pond last summer until we did pond maintenance and thereafter there was a sudden drop in the population. I have been purposely overfeeding the snails in hopes of boosting my population however I get tons of snail eggs but very few small juvenile bladder snails. Since I began my snail colony I have had approximately 20- 30 adult snails at one time. The population doesn't seem to grow despite my efforts. I also recently just purchased some Ram's Horn snails, again native to this region, that has been in a quarantine tank for two weeks struggling and terribly inactive.

I am a novice when it comes to the concept of GH & KH but I have tested my water and found my gH is at 22dgh & kH at 19 dgh. I understand that this is very hard water but I am a bit confused as to why things seem to thrive in my pond but struggle in my aquarium? Same water source. Could there be a mineral deficiency in my aquarium that Isn't in my pond?

 

The readings for GH and KH are okay for most plants, most invertebrates and a variety of fish. If any it's to hard for many fish, not for other lifeforms.

Same water source. Could there be a mineral deficiency in my aquarium that Isn't in my pond?

A pond is bigger than your tank and the bigger the body of water the more stable. The water source alone is not the reason why the tank and the pond work differently. There are dozens of factors.
You could put two tanks next to each other, both with the same water, substrate, plants and animals and still both could do very individually well/bad.

 

It could be a difference in lighting also.

 

The readings for GH and KH are okay for most plants, most invertebrates and a variety of fish. If any it's to hard for many fish, not for other lifeforms.


A pond is bigger than your tank and the bigger the body of water the more stable. The water source alone is not the reason why the tank and the pond work differently. There are dozens of factors.
You could put two tanks next to each other, both with the same water, substrate, plants and animals and still both could do very individually well/bad.

Do you have any thoughts on what I could try to be more successful? I tested my calcium levels and they were fine.

It could be a difference in lighting also.

The tank sits by a window and has 6hrs of aquarium hood lighting

 

Do you have any thoughts on what I could try to be more successful? I tested my calcium levels and they were fine.

Not really, sorry. Not a snail keeper.