Originally Posted by bigjay517
Opps, I did forget that. I have tested the tap water and I got 7.2 without letting it sit. I do not know if my water is hard or soft. I am using city water, not well water if that helps.
From this I would conclude that there is probably something in the larger tank that is raising the pH, as was suggested earlier in the thread.
The hardness, specifically carbonate hardness (KH) of the tap water will act as a buffer to keep the pH stable, within reason, so once established a tank usually remains fairly stable (same pH) if weekly water changes occur. Left alone, and depending upon the KH of the water, the biological actions in any aquarium will tend to acidify the water and lower the pH. The amount depends upon the KH value and extent of water changes.
Like iamntbatman, I don't know how much residue may be affecting this; a good scrub with vinegar and water of the filter plate and tank walls might help, then a good rinse.
You don't say what type of tropical tank, if you are thinking of a planted aquarium with tetras, rasbora, gourami, angels, catfish, loaches, etc., then a UGF would not be a filter of choice, and once it is in their you can't disconnect it without taking it out and tearing down the tank, so I mention this as a thought.