Does drop checker solution go bad?

[SupersoNick95]

I'm currently using an fZone drop checker with their provided indicator solution. However, This morning I wanted to re-install my Fluval C02 drop checker in my tank because I feel the white background makes it easier to determine the color. I went ahead and used the original fluval solution rather than the fzone solution to "double check" my c02 levels. I did all of this well before c02 and lights were on.

NOTE: Both of these solutions are premade. They do not require mixing with a dkh adjusted water. Both instructions say to add directly to the checker. the fzone solution is advertised as 4dkh, while fluval never discloses whether theirs is 3dkh or 4 dkh.

I noticed the fzone solution was lime green by the time the lights were on, but the fluval solution remained blue. It is still blue even 5 hours after c02 had turned on. Both drop checkers were in the same position in the tank.

I decided to remove the fluval solution and add the fzone solution into the fluval checker. I can now see it slowly turning green within about 30 minutes.

could it be that the fluval solution is a different dkh and affects the time it takes to make a reading? O r is it just bad/defective? 

Im currently riding at about 2 bubbles per second on my tank,.

UPDATE: I have waited a while and the fzone drop checker has turned lime green while the Fluval checker is halfway between green and lime green using the same solution. I hypothesize that the fluval checker has a smaller entry hole and this is why it is taking much longer to show changes in co2.

Edited January 12 by SupersoNick95

[knee]

Cant speak for anyone but I’ve used solution that’s I’ve had for about 3 years and it still changed color when co2 was introduced.