Page 1 of 2
Discus fry tank water hardness
Posted: Mon Jul 07, 2025 10:24 am
by polar
My Discus fry aren't growing like they should, and I'm thinking it's the water hardness. I've got a 40-gallon tank, 0 ammonia, 0 nitrite, 5 nitrate, pH 6.8, but GH is around 8. Should I cut it with RO water or just let it ride?
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 11:22 am
by Luckykeeper
Hardness at 8 dGH is a bit high for fry. I'd recommend mixing 50% RO with your tap to get it down to 4-5. Keep temp at 86°F, feed 4x daily with live baby brine, and do 30% water changes every other day. They'll bounce back.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 12:50 pm
by Honey
Luckykeeper wrote: ↑Mon Jul 07, 2025 11:22 am
Hardness at 8 dGH is a bit high for fry. I'd recommend mixing 50% RO with your tap to get it down to 4-5. Keep temp at 86°F, feed 4x daily with live baby brine, and do 30% water changes every other day. They'll bounce back.
Agreed, but watch the TDS too. If it spikes above 200, they'll stall. What's your substrate? Buffering with peat can help stabilize things.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 1:39 pm
by foxcape
Y'all making this sound like rocket science. My fry thrived in harder water, but I cranked the heat to 88°F and fed 'em blackworms like candy. Maybe yours just need a vibe check, polar.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 1:48 pm
by sealine
I've had luck with a drip system for RO mixing. Set it up with a 10-gallon reservoir, airline tubing, and a valve to control flow. Takes the guesswork out. Also, what's your lighting schedule? Too much can stress 'em.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 2:53 pm
by polar
Thanks for the tips, everyone. Gonna try the RO mix and bump the temp. Substrate's bare bottom, lights are on 8 hours. I'll report back.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 3:04 pm
by Silvan
Bare bottom's solid for fry. Less junk to mess with. You got a sponge filter or HOB? Sponges are chill for bio, but HOBs move more water. Just don't let it suck 'em up.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 4:28 pm
by purered
foxcape wrote: ↑Mon Jul 07, 2025 1:39 pm
Y'all making this sound like rocket science. My fry thrived in harder water, but I cranked the heat to 88°F and fed 'em blackworms like candy. Maybe yours just need a vibe check, polar.
Heat's key, but blackworms can sketch out newbies. Stick with brine shrimp if you're not sure. Also, what's your water change routine, polar?
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 5:45 pm
by LunaSky
RO mixing is the way. I use a 3:1 ratio of tap to RO for my fry tanks, keeps GH at 4.5 consistently. Are you using any supplements? Calcium can help if you're cutting hardness too aggressively.
Re: Discus fry tank water hardness
Posted: Mon Jul 07, 2025 7:11 pm
by chippy
My fry tank's at 7 dGH, and they're fine. Maybe it's not the hardness. What's your feeding schedule? Overfeeding can mess with growth too.