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Trouble with tanks, should I use RO water?

954 Views 6 Replies 4 Participants Last post by  Kim
I have recently started keeping fish and I am pretty sure there's something wrong with my tap water. I cycled my 20 gallon a few weeks ago and I added 3 albino cories, 6 rasboras, and my male betta Comet. I checked the water parameters everyday and they were always good:
Ammonia: 0
Nitrite: 0
Nitrate: 2-5
Water Hardness: 180ppm (highest my test kit went so it could be a little higher)
Ph: 8.2

Though everything on my tests seemed fine, my rasboras started dying. Every 5-7 days I would find one dead. My other fish seemed fine though. I went on a 5 day over Chistmas and when I got back another rasbora died leaving me with 2 and my betta had terrible fin rot.

I checked the water right away and everything was perfectly normal. The only reason I can thing of that could be harming my fish is that there's something bad in my tap water that I'm not testing for. If this is the case, I was thinking that I could use RO water to help lower the levels of whatever is hurting my fish.

I know that you can't use pure RO water, so how much should I use in my tank? Also, where is the most affordable place to buy RO water and about how much does it cost?
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If you want to use RO you cut 50/50. It is also EXTREMELY important you mix this up the EXACT same way every time to avoid fluctuations in ph and gh which can easily shock fish.

However, I wouldn't assume that would be necessary or even help at this point..

What size was your tank? Albino cories can get quite big.

What are you using to test your water? Drops/strips brand? How long has it been set up? How much of a water change do you do per week? What filter are you running? What did you use to cycle the tank?
My tank is a 20 gallon long which I read in several places was good for albino cories. I am using the API liquid test kits and I use the strips to test for hardness. I have an aqua clear 30 filter that's been running for about 1.5 months or so.
I cycled my tank using 3ppm pure ammonia and I put in tetra safestart to help speed up the cycle. It worked great and my tank was cycled in 2 weeks with no nitrite ever and the nitrate only went to 5ppm at its highest.

I only added fish about 3 weeks ago and I went on a trip for the last 1 of those weeks so I haven't done a water change yet. (I know that's really bad so I'm doing a 25% one today.) There was still no ammonia or anything when I tested yesterday so my water isn't too bad yet.

Do you think I should try doing 25% twice a week and see if that helps my fish before I use RO water or anything?
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RO can be a pain to get exactly right every time. I would try filling a stocking with peat moss and see if that removes whatever is causing the fish deaths (peat moss binds lots of minerals). It will also slightly and naturally lower the pH of the tank without any dangerous spikes. The moss will release some tannins and stain your water.

25% changes 2x per week seems like a lot for a 20g, what is your substrate and do you have live plants?
I have ecocomplete substrate and a good number of live plants. I will try using peat moss like you said. Do they sell it at Petsmart and how much should I get?
I have ecocomplete substrate and a good number of live plants. I will try using peat moss like you said. Do they sell it at Petsmart and how much should I get?
Actually you're more likely to find it at a gardening store. Sphagnum peat moss is fine, just make sure the word "peat" is on there somewhere. A small bag is good, that should last you a few months at least.

One weekly 25% water change should be plenty for your tank.
How did you acclimate the fish? Your tap water is hard and has a high pH...without proper acclimation, the fish may have gone into shock and died. Also, did you add water conditioner to remove any possible chlorine/heavy metals? Do you drink your tap water (just wondering if you may have some sort of bacterial issue)?

If you do find out that something is wrong with your tap water, RO water would work just fine so long as you buy a balanced mineral mix to buffer the water and replenish essential minerals. I'm not sure where the best place to buy is, but if you plan on keeping tanks long-term, it may be worth it to just buy a RO unit (I've seen some on e-bay for decent prices). If your tap water turns out to be fine and you just want to lower the pH a bit (which may be helpful for some of the species you are keeping), you can just use some RO water with your tap (since your tap has minerals already, there is no need to add a supplement).

Hope this helps and you get the issue sorted out soon!
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