Introducing fish to perculas

[leezard]

You should maybe get rid of the conches as your tank is too small to give them enough to eat for very long.

Hm. Well. They said it should be fine.... and if not, apparently I can feed them seaweed wrapped on one of the rocks on the bottom?

And you are looking at putting five fish into a twenty gallon?

We were at first, but have been told to back off a little on the bioload. We're more just deciding between these what we want the most-- and if the twospot will be a huge problem, he'll probably be the first off our list.

Bioload is extremely high regardless and we do not dare miss a weekly water change of about 20%.

I sticking with about 10% per week... so far has worked out, but I'm sure that may change once we add more fish!

[Pier Pressure]

Well I am no expert by any means. You may want to google conches and see what it says online. Sadly sometimes people will mislead you at an lfs just to make the sale, or because they themselves do not know any better. Actually you might be okay with the supplemental feedings. I was just told my tank was too small for a conch.

[leezard]

A google search comes up with pretty much the same info, but alot of it is vague. I know another girl who has one in her... I think it's a 10g nano, and it's doing swell. These guys aren't supposed to get big, though -- yet there are varieties of conches that do get much bigger. Maybe those are the ones you were told about?

These guys didn't make money off of the conches, though -- there was a mistake in shipment and they got too many of them. I paid $4 each.

[Pier Pressure]

You should be okay with the small ones but I have read even in a big tank they do better with supplemental feedings. So as long as you are supplementing - they should be just fine. I had not realized they were the dwarfy kind!

[naesco]

Too many snails and no room for conchs. Return most of them to the LFS for a credit. By adding algae to your tank you are simply adding to the bioload.

Sorry to say but the likely cause of the ph spike is the death of one or more of them to starvation. Have you checked your ammonia? Another cause would be insufficient current for oxygen exchange.

You have a nano tank which is what I have at the office. I have two false percs and would not add anything else.

You are on the right track to avoid aggressive fish. Avoid the dottyback for that reason. Avoid the firefish unless you have a covered tank and avoid the 2spot as they have a very poor survival record.
Consider a yellow goby or a passive small fish with a good survival rate.
Thanks for asking for advice before you buy.
Good Luck