Tropical Fish Forums

[Jimbob]

I have had a great deal of pleasure from fish keeping over the years and through the very positive experiences I have had a my local stores place Maidenhead Aquatics at the top of my list for equipment, live stock and ongoing sundry goods. The staff are of the highest order and I have nothing but praise for their time, patience and expertise.

One area however that I have struggled to find consistency with is the question of effective management of my soft-water tank. I have no criticism whatsoever of the advice given from different staff at different stores but would like some clarity on how best to manage supplementing RO water to achieve stability before using it for my regular regime of water changes (36 litres which is 25% for a 144 litre capacity aquarium).

I had been using Tropic Marin re-mineral supplement for freshwater which provided me a stable product at 26c of 7.2 pH, Gd 5, KH 4, 0 No3, 0 Nh3, 0 No2 and TDS of 145.

However, there is conflicting advice as to whether the supplement provides all the mineral replenishment my fish require and a recent outbreak of bacterial disease with no appreciable change in water quality does lend itself to supporting that theory. (Water parameters are TDS 182, 7.2 pH, 5 Gd, 4 KH, 10 No3, 0 No2 and 0 Nh3.) I have treated, with varying degrees of success, using Waterlife Myxazin. Fatalities have been x1 Nannostomus marginatus and x 4 Paracheirodon axelrodi over a three month period February - April 2012 and none of those fish were older than eighteen months.

Moving towards using tap water instead of a mineral supplement does appear to make sense but the advice differs; one suggestion has been to use ratios to the equivalent of 25 litres of RO with 2 litres of tap water whilst another suggests a mix of half and half.

There are marked differences in the potential stability of these ratios; particularly around the buffering properties of the mixed water:

The 25:2 ratio produces water with a desirable 7 pH but an unstable 1 KH and 1 Gd which I am concerned will produce problems with pH fluctuations.

A 1:1 ratio produces a highly desirable stability of 4 KH and 6 Gd but an undesirable 7.4 pH

I am testing with JBL liquid cross referenced to Interpet tablet kits and my local retailer has confirmed the accuracy of all my readings.

The tank has sand substrate and is currently stocked with a controlled breeding colony (about 6 adults and 12 juvenile) of Antentome Helena, x3 Corydoras panda, x5 Nannostomus marginatus, x8 Paracheirodon axelrodi, x4 Otocinclus and x1 Hypancistrus zebra.

The tank has been running since April 2010 on a Rena XP3 filter (nozzle outflow not spray-bar) maintained at 26c away from direct sunlight with ambient room temp of 20c. Five hours T8 florescent lighting per day and heated with a Rena 200w Smart Heater. Have been oxygenating with a pump and air-stone since March. The tank is lightly planted with Cryptocoryne wendtii, Cryptocoryne wendtii
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[diademhill]

How can RO be raising the pH?

Are you allowing the tapwater to stand for a few hours to degas before testing?

[Osprey]

If I read the post correctly, the RO is lowering the pH so that it is neutral- or closer to it, anyway.

I would suggest trying the 1:1 RO:tap ratio; stability is more important than the pH (Pretty sure you know this already) and a pH of 7.4 is not liable to cause any health issues with the fish you currently stock. If they stop spawning, then you may need to experiment further to find the right balance.
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[diademhill]

Sorry, I read the tank water as tap water.
What are the tap parameters please?

I agree that 50/50 is probably fine.

[Jimbob]

Hi and thanks for both responses. Tap water is quite nasty here - TDS 230, No3 40, pH 7.6, Gd 10, KH 8.

The RO readings detailed in my first post were taken after 24 hours at the desired temp so allowing for the 'bounce' factor.

The 1:1 ratio is starting to feel like the better option not least as I can reduce by half the amount of RO I am producing which means less waste (although I do collect and recycle for car washing and garden use).

Will plan to do a series of 5% water changes over the next ten days to ease the system in to the change in parameters.
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[diademhill]

2/1 might work and you could start with this and then go 1/1.

You could always add a tiny bit of cuttlefish bone for the snails.