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Hi everyone! I am new to this forum. I live Minneapolis, MN, U.S. I have been keeping fish since 2001, but have failed at all of my attempts to keep happy Corydoras. My problems with cories have been short barbels, followed by "pale pink patches" and death. My three main questions are about substrate, tank mates and cory species choices for high pH.

This is kind of long, since I don't know which of the following parameters is important.

I have 3 tanks: 10 gallon (since 2001), 55 gallon (since 2002), and a new 75 gallon that is thoroughly cycled. I just moved most of my "mean" fish to the 75 gallon. I intend to use the 10 gallon as a quarantine tank from now on. I want to make my 55 gallon into a tank for "friendly fish." This is where I want to keep cories. The tank is 48" long x 13.5" wide x 21" tall.

Substrate: The 55 gallon has a substrate of fine gravel, but with sharp edges - i.e. it's not like those bags of polished gravel you would buy at a pet superstore. The bag says "Filter and abrasive sand," and it's from a quarry in Wisconsin, U.S. It is the cheapest substrate to get at my LFS when one buys a new tank package. After looking at cory advice on other sites and the need for smooth edges/sand, I was thinking of scooping out about 33% of this substrate and replacing it with smoother gravel or sand. I would rig up some kind of barrier so the two wouldn't intermix right away. I suppose I could replace all the substrate, but it's been with the tank so long, I worry that might be traumatic to the tank environment. I have some healthy Vallisineria now, but not for for long, since I moved the mega-light to my 75-gallon. I can deal with new plants later.The tank now has 2 basic "came with the tanks" strip fluorescents. So here's the question: Should I change part of the substrate in this 6-year old tank, or all of it at once?

Tank mates: The tank mates I intend to have remain in this tank are my 2 ancistrus (mature and juvenile), my 2 farlowellas and the 3 khuli loaches. Still to be moved (which will happen soon) to the "mean tank" are 12 small tiger barbs. I haven't decided on what else to add after the tank, but they will be peaceful mid to upper-dwellers. I assume I should move the tigers before I add the Cories. My question is, I have one (don't ask) almost mature red rainbow. Can I add some more red rainbows? Do they get along OK with cories?

Water: I live in Minneapolis, which has odd water issues. Water from the tap is well over 8.5 pH. I add buffer, but it seems it never gets to 7.0. I am a little peeved right now, because I just bought a test kit that didn't have hardness or alkalinity tests. But basically, I always add buffer during water changes, but still have to struggle to get the pH near 7.0. My last test kit was always telling me to buffer up. I do water changes every 10 days or so, and my nitrites and nitrates are always zero. My question here is, are there any cories that are tolerant of higher pH?

Did I miss in your post what kind of cories you have?

I have peppered cories in a 20 long with carib sea tahitian moon sand and their barbells are fine. I am going to change it one day tothe carib sea moonlight white sand tho cause it's softer and I can see them better on that I think.

My peppered cories are very hardy and doing well. So I was curious what kind urs were. Also if you feel ur sand is abrasive I would def change it out. You can do it a 1/3 at a time if you are worried re upsetting ur biological filter.

Also, in my opinion, for what its worth... , i feel messing with the ph is dangerous to the fish, too much flucuation. I have always heard and read that fish will adjust to the ph in ur tank altho 8.5 seems high to me, that's perfect for some cichlids and stuff!

There is a temp link in here under catalog search i think, so maybe there is a ph link?

If you intend to change part of the substrate to sand, it would be easier to do it all in one hit & as long as most of the mature water is saved should only be a minor disruption to the tanks, overall stability.

I think red rainbows should be ok - move the tiger barbs before adding corys though

I can't tell you about corys that prefer high alkaline pH - that's beyond me but there are things that can be done to alter water chemistry to softer, more neutral, or slightly acidic conditions like the addition of bogwood & peat (in a mesh bag) as well as chemical pH changing products.

Fish do adapt to local water conditions but this should be over a lengthy period of time & may not be ideal for long term health &/or breeding aspirations. Corys bred locally should be ok as they would be very used to the water you have - do the lfs sell wild imported or locally bred or commercially bred corys? are there local breeders near you?

Most Corys and especially C. paleatus adapt to pH as high as 8.5.
Many of them can not successfully spawn or have eggs hatch in such water but C. paleatus can.

andywoolloo wrote:Did I miss in your post what kind of cories you have?
Also, in my opinion, for what its worth... , i feel messing with the ph is dangerous to the fish, too much flucuation. I have always heard and read that fish will adjust to the ph in ur tank altho 8.5 seems high to me, that's perfect for some c*****ds and stuff!

I had schwartzii when I first started. They actually lasted the longest, in my PetSmart 10-gallon with polished gravel. Hmmm. Anyhow, I also had punctatus, or something like that - they had little round dots. My last attempt was with very young pink ones (sorry, don't know the name); I just went with really inexpensive ones, given my past experience.

My understanding is the buffer doesn't really "mess with Ph." I heard it mainly helps to stop wild Ph swings.

Thanks for the encouragement on the sand front.

Richard B wrote:If you intend to change part of the substrate to sand, it would be easier to do it all in one hit & as long as most of the mature water is saved should only be a minor disruption to the tanks, overall stability.
Corys bred locally should be ok as they would be very used to the water you have - do the lfs sell wild imported or locally bred or commercially bred corys? are there local breeders near you?

Thanks, I'm leaning towards full sand the more I read about processing sand. I'm certain my LFS has locally bred cories, but the water in most of suburbs (home of my LFS) is from a different source than my city water. I will make a point to ask about obtaining get some hardy urban cories.

More on substrates: In my new 75-gallon I have a potting soil under layer (for the plants) with the Wisconsin gravel on top. Could cories handle a soil underlayer under the sand? Come to think of it, I could add a hefty dose of peat to the soil underlayer to try and lower the pH.