Help! Lost two fish within a day. Is something wrong?

[WhiteWine1nTheSun]

We set up a new tank at the beginning of May and cycled it for 4 weeks. 2 weeks ago added 4 platys. They've been great. Water is testing well, although at the acidic end but my water is quite acidic anyway.

On Saturday we got 2 guppies to go with our platys. Sunday morning one started looking sick and then died within an hour or so. I thought it might have been the shock of the move. We got stuck in traffic and he was in his bag for an hour. The other one is fine.

Now just got home to find one of our platys has died today. Could just be coincidence but seems a bit strange as they have been fine.

Could we have brought in a disease, or is it likely to be a tank problem? We did a water change Saturday morning as usual (10%)

It's a 70 litre tank. pH is 7.4. Any suggestions?

[EauRouge]

Yes, the guppies could have brought something in- for this reason it's always advisable to quarantine new fish- but it's unlikely that your old fish would have died so quickly from a new illness. What are your water readings? A pH of 7.4 is not acidic, it's pretty much neutral; has it changed?

[WhiteWine1nTheSun]

I don't think it's changed. I hadn't tested it for a week, and it's been around 7.4 every time I've done it, although I only bought the kit a couple of days before I bought the platys.

Other fish are all looking OK tonight so I'm hoping it's a coincidence. I'll come back if there are more problems in the next few days.

How do you quarantine them? Do you need another tank set up somewhere?

[WhiteWine1nTheSun]

Back again. I lost another platy today. DD phoned after I'd gone out to work so spent the whole day worrying about it and googling it. I'm sure there's something wrong with the water. In the last couple of days the stones have all gone green and there's a lot of plant / food / poo debris in the tank.

Tonight I have done a 30% water change, and also removed both plants. One of them was falling apart and may have been blocking the filter /decomposing. The other looked healthy but had developed hairy algae on it.

I've also been out and bought a new filter. The one I got with the tank seems to be a bit faulty and sometimes seems to stop. Not sure how long for, but when I was doing the water change, nothing was coming out of it. I'm beginning to wonder if it hasn't been working since Saturday.

After I bought the new one I turned the old one on again and it worked (typical!) so I've left the old one running and put the new one next to it because I read that the new one won't have the bacteria in it straight away. Is that right? If so how long should I keep both filters running?

Anyway I have a slightly cleaner looking tank now and 2 platys and 1 guppy swimming around happily, although occasionally getting blasted across the tank from the strength of two filters!

I read that it's best not to add any food for a day or so if you suspect the nitrate (?) levels are too high. Is this good advice?

Also should I do another 10% water change each day for the next few days until I'm sure the new filter is doing its job? I've read so much conflicting advice today I can't remember what I've read.

Thanks x

[SillyTilly123]

Have you tested ammonia, nitrite and nitrates? Hairy algae i believe is a sign of high nitrates. If the nitrates are particulary high (for example 80) the a 50% water change would bring them down to 40 iyswim 40 and under is recommended.

You can not feed for a day or to to stop nitrates building up as fast but a water change is the best way to remove nitrates.

Is your tap water the same as tank water (mine goes from tap 6.4 to tak 7.6) and a few weeks ago without thinking about it i did a 75% water change and a few of my fish dies because of the change in PH (wont be doing that again in a hurry)

Re the filter: can you not put the media from your old filter in the new one?