Fish dropping like flies - water tests all normal. AquaSoil issue?

[flix_cw]

Any help please:

I recently moved house (and my fish) 4 days ago, and in the last 12hours I've lost 4 fish (glowlight tetras and harlequin rasbora) and my dwarf gourami is looking vv sick.

I had a very established 7yr old heavily planted 56L tank prior to the move, i now have a 130L tank. The canister filter wasn't switched off for more than a few hours. I haven't moved far so the mains water is the same.

I've used an API Master Test Kit and the results are as follows:
Ammonia - 0
Nitrite - 0
Nitrate - 5ppm
pH - 7.6

The one thing that is different is that i bought AquaSoil from Maidenhead Aquatics (https://www.fishkeeper.co.uk/product/aquasoil) and have that as a base layer substrate, capped with gravel from the old tank. Might there be (a) compound(s) that it's leeching that the test kit doesn't pick up? Has anyone else come across this issue? I'm doing 50% water changes 2x daily.

Any thoughts much appreciated.

 

[DutchMuch]

Old tank syndrome...?
but if you just bought some new aquasoil and added it to an established tank it will leach ammonia.

 

[Chippers255]

Do you know what your PH was before and after? I found adding Fluval Stratum drastically dropped my PH. You may not be seeing a fluctuating PH any more but the initial shock to the fish could be lingering.

 

[flix_cw]

Thanks everyone. Water parameters still the same, but even all my plants have died a death too! Definitely not the desired effect all round. This weekend i am tasked with breaking down the tank and starting all over again...

 

[StevenF]

has your water hardness (GH), or alkalinity (KH) changed from your old place to new? Plants need 15 elements to live (excluding light and CO2) If you moved from a place with hard water to a place with very soft water your plants could die. Also note that the 15 elements plants need are typically not toxic at normal level. However if they go up for any reason they could suddently become toxic to the fish. Have you been using any water conditioners and fertilizers? If yes please list them. Also how much water do you change out in a week?

Adding the aquasoil may have not helped. Sometimes these plant substrates do leach too many elements into the water. And sometimes they can contain ammonia sulfate, ammonia chloride or even ammonia nitrate. These forms of ammonia may not be detected by some test kits. I have never used any plant substrates and I don't have any specific information or experience with the one you used. Some are probably better than others.