Possible substrate problem

[MLBfan]

This is from my 29 gallon with firemouths:

From a different thread I started

substrate: CaribSea Seaflor Special Grade Reef Sand 15 lb

Actually that is for marine tanks, that substrate. It would harden your tank water, and every time you do a partial change your hardness would go up and down.

If you look for threads by me, you'll see how I do planted tank substrates, and why I do them that way. If you have questions about it, just ask.

Dave

Ok, now I fear I may have a bit of a fiasco on my hands.


So, the substrate is a marine substrate I know, but it says it is also for African cichlids (the tank was originally going to be a Tanganyika setup, but I changed my mind), so with that I got my water tested originally at 7.8 pH and decided that it would be fine given that the fish are not from the wild and the tank are hardy, I drip acclimated these guys: Params went:
pH-7.8 GH-11 KH-6 on 04-05-2012
pH -7.4 (suspect that addition of a little driftwood did this) GH-6 KH-4 on 04-09-2012
pH- 7.8 GH- 11 KH- 6 on 04-12-2012 (A fish died a day after that)
ph- 8.2 GH 13 KH 7 on 4-13-2012
pH -8.0 GH-18 KH-9 on 04-16-2012 (Fish died on that day)
ammonia, trites and trates remained 0/0/<25 through the entire time

Some human error while testing could have messed up the results a tiny bit, but now I'm wondering if the substrate did this, I haven't done any water changes yet because the params remained good and I didn't want to upset them because they were already super freaked out. However I did add some water in to fill it to the water line. Anyway, should I change substrates? If so, how do I do that and keep my fish alive and well?

[Aeonflame]

The main issue is not with the water hardness, but in the fluctuation in parameters.

[Lady Hobbs]

My guess would be the sand. It is meant to buffer the water and keep it on the high side of pH for africans.

[MLBfan]

So should I change substrates?

[Aeonflame]

I would advise it. Get something inert that will best suit the stock you have now. You can always dry and store this substrate for later if you need it.

[MLBfan]

Ok, so how can I change it without disturbing my fish by getting a big drop in hardness or pH?

[Aeonflame]

Change the substrate and leave the water. Then gradually do small water changes over the course of the week

[scotchbonneteater]

I'm new to this but could you suck the sand out with a syphon and add cleaned gravel by handfulls ?

[MLBfan]

I think I'll siphon the sand out , do daily 10% WCs, and later in the week put some gravel in.

[MLBfan]

Actually, is there another way to remove the sand? I'm afraid doing this will also remove a lot of water which I will replace and the pH and hardness will be all over.