I will be upgrading my 50 gallon to a 75 gallon next month. The water in the tank is always ph/6.8, gh/4-5 dh, kh/3 dh. All of my other tanks are ph/7 with the same gh and kh. The 50 gallon has an undergravel filter with 2 50 powerheads and an emperor 400 hob. My 1st question is I want to switch from gravel to sand but I will lose the UGF. Do you think the UGF is what's helping keep the ph down? The only other tank I have with a UGF is the 29 gallon. The reason I ask is because I'm delving into the world of discus and will be acquiring 3 more and want the ph to stay at 6.8.
My 2nd question is the best way to move fish and water as not to stress the fish tremendously? I could probably drain most of the water out of the 50 into the 75, add some fresh water, transfer the fish, then the remainder of the water out of the 50 into the 75 and top off with freshwater. I don't want the ph to go up too quickly due to the discus.

is there drift wood and stuff in the 50 that you don't have in other tanks? because to my knowledge, wouldn't the driftwood make the ph lower?

also, since they are s. american cichlids, don't they generally prefer a ph of like 6.2 or so? which isn't bad anyway... I've never kept discus, so I don't know for sure, but I would say just drain most of the water, keep as much stuff as you can out of one, to the other, and just make sure they're the same temp, and they should be fine.

If gary has been getting discus in the mail, which get shook up, and are in the dark for day(s) then moving a fish from one tank to another should be ok, at least in my head.

I'd wait to get a second opinion though in case I'm wrong.

When you come to change tanks over i would put as much of the water from the 50 as possible in the 75 as you can then i would top up with fresh water, also having as little water as possible left in the 50 will make catching what fish are in the tank, a lot less frantic thus reducing any stress imposed on the fish

Good tip on catching the fish clunk. Thanks.

No worries mate, as the less stress the better the change over

Exactly.

My livebearers are dropping like flies. I don't what the problem is, but the discus and my cats are doing great. I test the water weekly before I change it and the parameters are right where they should be.

Are they getting harassed or bullied ?

Not theat I have witnessed. They have all come down with the symptoms of dropsy. Near the top, listless, bloated with the pinecone look. I have tried salt, heat (88*F), Melafix, Pimafix, API general cure. Nothing has cured them. It seems to just be the livebearers that get it.

Funky,
I think the water is too soft and acidic for the livebearers.
mike

mpp mentioned what I was going to point out. Most of the common livebearers that are found in the hobby (guppies, mollies, platies, swordtails, etc.) do much better on hard water with salt in the water (this is especially for mollies who are more fit for brackish to marine water). Because they are being kept in soft water, then they are more prone to disease and stress. They are also generally more line bred than other fish, which makes them more prone to disease.

I was wondering if the kh and ph had something to do with the livebearers not living. I can't keep panda cories alive in that tank to save my life either. That may also explain them not living. I think I've had at least 50 panda cories and I have 1 alive. The sterbais, arcuatus and adolfois all do well.